CHINA–SOUTHEAST ASIA RELATIONS: A RETROSPECTIVE OF CHINA’S TRIBUTARY SYSTEM

This article attempts to describe the ideology, politics, and implementation of China’s traditional tributary system to better understand its suzerainty over states, specifically in foreign relations. Through this system, China, which is considered to be the superior state (shangguo), will protect the sovereign states in its orbit. In return, the sovereign states have to present tributes to the Emperor of China, who is regarded as the Son of Heaven (tianzi), as well as recognised China’s greatness and power. This study involves a qualitative analysis based on official Chinese historical records as well as scholarly studies on the effectiveness and limitations of the system. This article also covers countries in Southeast Asia that adopted tributary systems. This region is still poorly defined, and the limited number of studies, especially regarding its history and intra-regional development prior to Western powers' arrival. The research findings proved that China’s tributary system in the Southeast Asian region is dynamic relationships. Hence, it is suggested that researchers should look at the system within a broader framework to understand its implementation. Although the practice of the tributary system is Sinocentric, it is neither static nor monolithic. Conversely, the tributary system has a well-organised, neat and well-established mechanism that results from mutual understanding between China and its protectorates. 
Keywords: tributary system, China foreign relations, Son of Heaven, Mandate of Heaven, China-Southeast Asia tributary relations


Introduction
When describing China's foreign relations, it is important to understand its tributary system's general concept and development, which formed the basis of its relationship with other countries. Hamashita (1988Hamashita ( , 2008 insists that it is necessary to understand how every region and country in Asia tried to adapt to China's tributary system, which Hamashita was regarded it as very influential and intertwined with China's interactions with the foreign world. Unlike the Westphalian system, it was not based on the principle of equality of sovereignty, but on the concept of overlordship over vassal states (Vuving, 2009). Briefly, the system worked as follows. China was considered the highest government (shangguo《上国》), and the emperor was believed to be the most noble and powerful ruler (yiguan shangguo liyi zhi bang 《衣冠上国，礼仪之邦》). It was also believed that the emperor's home was the centre of the universe (centralia, zhongguo). Hence, other countries, as vassal states (shubang 《屬邦》or shuguo《属国》), were expected to abide by China's command. To establish a relationship with China, the vassal states were required to pledge their loyalty and acknowledge China's suzerainty as well as present tribute to their overlord. Due to the complexity of the protocols and regulations adopted in the system, some researchers have claimed that China's attempt to control its vassal states led to their refusal to comply with the system (Perdue, 2015). Ford (2010), Hevia (1995Hevia ( , 2009, Kang (2003Kang ( , 2012, Lee (2017), Smith (2013), Wills (2010), S. Zhang (2004), Y. Zhang (2001) and Zhang and Chang (2018) have suggested that the implementation of the tributary system needs to be studied more comprehensively. Specifically, they have argued that the tributary system should no longer be viewed from the perspectives of scholars such as Fairbank (1942Fairbank ( , 1968, Fletcher (1968), Lien (1968), Mancall (1968Mancall ( , 1984, Rossabi (1983) and Wang (1965aWang ( , 1965bWang ( , 1968Wang ( , 1995Wang ( , 2005aWang ( , 2005b, who focused on the importance of the tribute system as the traditional Chinese system for managing foreign relations. Instead, the authors suggested that more in-depth and thorough research on the tributary system's structure and function is needed. As Perdue (2015) claimed that China's tributary system was far from perfect because it did not have a systematic mechanism. In addition, he added that the tributary system failed to receive support from the protectorates. This article adopts a Chinese perspective to explore beyond the philosophy, concept and implementation of the tributary system and determine these allegations' truth. As Vuving (2009) has suggested, China's external relations should not be perceived from a Western perspective because the West has adopted a Westphalian system with different values and viewpoints. Vuving (2009, pp. 73-74) states, Unlike the Westphalian system, which is characterised by equality between states, the Chinese world order [tributary system] is a hierarchical system in which China is the suzerain, the world centre, and the superior state, while other states are its vassals, tributaries and subordinates.

Literature Review and Methodology
Several studies have been conducted on tributary relationships. Fifty years ago, Fairbank (1942Fairbank ( , 1968 conducted his pioneering study of the tributary system that structured the relations between China and Southeast Asia, leading to a world order that was both Sinocentric and orchestrated by China. Since then, his work on the tributary system has continued to be discussed by Chinese historians such as Mancall (1968Mancall ( , 1984, Stuart-Fox (2004), Wade (1994Wade ( , 2008, Kang (2003Kang ( , 2012, Wang (1965aWang ( , 1965bWang ( , 1968Wang ( , 1995Wang ( , 2005aWang ( , 2005b and Zhang (2015). Zhou (2011) tried to present an important and stimulating application of game theory and patterns of interaction to China's traditional diplomacy with its neighbours. However, his analysis contradicts the realistic expectation that China, possessing greater strength, tried to dominate smaller countries in the context of foreign relations. Zhou's explanation of the tributary system deemphasises the cultural explanation, according to which Confucius's moral teachings played a large role and emphasises conflictual interaction processes that led to mutual respect between China and its neighbours. Subsequently, Wade and Chin's (2019) book aimed to challenge the cliché view that the China-dominated regional hierarchy had been stable and peaceful, but it raises questions about the applicability of hegemonic stability in a non-Western pre-colonial context. The hegemony of China was not sufficient to bring economic and political stability to pre-colonial Southeast Asia. Regional trade was never completely open, and inter-state relationships did not ensure long-term stability among Southeast Asian countries. Thus, Womack (2012), who explored aspects of China's foreign relations with Southeast Asia that involve China's tributary system, suggests that China's tributary system's history needs to be reviewed to gain a better understanding of the system. China's position as the centre of government in Asia is more fundamental to its external relationships than its asymmetrical power between China and other countries or the fact that some dynasties and emperors pursed policies contrary to the tributary system. This is because Southeast Asia has long been an integral part of the China-centred tribute system (Chang, 2005;Nakajima, 2018;Niu, 2003;Stuart-Fox, 2004;Wade, 1994Wade, , 2008Wade, , 2019Wang, 1998aWang, , 1998b. Although much research has been done on the tribute system, few studies have focused on the Southeast Asian region or adopted a historical perspective. Some analysts have described China's relations with Southeast Asia as either part of a traditional Confucian tribute system or, more recently, as part of the Western concept of a sphere of influence. Examining and comprehending the many facets of the historical processes that have linked these two regions will provide context for, or otherwise illuminate, aspects of the contemporary and future relations between China and Southeast Asia, as suggested by Wade and Chin (2019).
The methodology of this study is based on qualitative analysis and empirical evidence related to China's tributary system and external relations with Southeast Asia in general. Data are collected from scholarly books and articles on China's foreign relations involving the tributary system and classical Chinese books from the Han Dynasty related to protocols and customs introduced during the Ming Dynasty. During that time, China's tributary system reached a period of maturity, especially with the Southeast Asian region.

Ideology of the Tribute System: The Tianzi and Tianming Doctrine
According to Fairbank and Goldman (2006), China often adopted a Sinocentric cosmology and considered itself to be the centre of world civilisation as it boasted a history of advancement that spanned more than 5,000 years, making it the oldest civilisation in the world. Until the middle of the Qing Dynasty , it was still perceived as the most powerful country due to its age, culture, vastness, level of advancement and location in Central Asia. As Samuel (2015) states, China believed that it was the centre of the universe (zhongguo), and the emperor, as tianzi (Son of Heaven《天子》), had de jure-although not always de facto-rule of the world. Since the emperor had received tianming (the Mandate of Heaven《天命》), he had to rule fairly and be a role model to all mankind. This is clearly evidenced in a statement made about Emperor Yongzheng (r. 1723-1735): Among the characteristics which allowed a king to govern successfully was his ability to protect and show his generosity to all mankind. A king must always act to care and provide a million reasons for his people to be thankful and happy. This was one way for his country to unite and his name should be engraved in their memories for eternity. Since his dynasty had received the mandate from heaven to rule, it should continue to spread love and protection to all without discrimination.
Why should a country be discriminated just because it was not China? (Qing Taizong Shilu,

la])
China identified itself as the only centre of civilisation because it practised the values and philosophies of Confucianism, which emphasises harmony in society through noble moral relationships. The principles of Confucianism include good tradition (li《礼》), justice (yi《义》), obedience (zhong《忠》), charity (dao《道》), humanity (ren《仁》) and a belief in good morals (de《德》). Fairbank and Goldman (2006) conclude that China had built a relationship with foreign countries (i.e. 'barbaric' countries) whereby it was revered not for its military prowess, but for its cultural supremacy. Upon defeating the Ming, the Qing Dynasty (1644-1911) retained all the institutions from the previous dynasty in order to gain the acceptance of the people (i.e. those of Han ethnicity) and to prove its claim of continuity of the previous administration.
According to a classic Chinese Shijing (The Book of Poetry) dating from about 1,000 BCE, putian zhi xia, mofei wangtu, shuai shi zhibian, mofei wangchen《普 天之下，莫非王土，率士之宾，莫非王臣》(No land under heaven does not belong to the king; no people within the king's land boundaries are not owned by the king). The notion of the state's or king's ownership of land was dominant throughout the imperial period in China, as well as in other Eastern and Western countries, in pre-modern and modern times. In addition, China believed that there were four groups of uncivilised countries-Xiyi in the west, Beidi in the north, Nanman in the south and Donghu in the east-all of which had not achieved a level of civilisation like China's. It was more advanced than other countries in the Neolithic Period (3000 BC-1500 BC), covering the times of Yangshao (5000 BC-2700 BC), Longshan (3500 BC-2000 BC), Majiyao (3300 BC-2050 BC) and Hongshan (4000 BC-3000 BC). It is common knowledge that China is the only country in the world with an established writing system that is more than 3,000 years old, supporting its claim of superiority.
At first, China believed in isolating itself to protect and conserve its civilisation and preserve its superiority over other polities. It had no wish to contact the world beyond its borders (Kobkua, 1997). However, in the 5 th and 6 th centuries, the tributary system began to spread across multiple continents. Additionally, foreign countries had begun to show interest in establishing economic and trade relations with China. China eventually capitulated but stipulated that those wishing to forge a relationship with the country should agree to present tribute to its emperor. For example, during the time of Emperor Han Wudi (140 BC-86 BC), the Han Dynasty was acknowledged by ethnic groups, feudal leaders and other territories within China. These groups presented tribute to Emperor Han Wudi on a scheduled basis in order to obtain blessings of security and protection, which, Depending on the situation, could range from a message of sympathy from the Chinese emperor on the occasion of a natural catastrophe to the dispatch of Chinese troops to the aid of the recognised ruler of the tributary pact against either internal or external threats. (Hsu, 1960, p. 4) This reflects the Han Dynasty's emphasis on the political rather than economic aspects of the agreement. Above all, China was firm about being the sovereign state, and tribute from a shebang, or a country deemed less civilised, was an important aspect of Confucian politics (Zhang, 2015). The shubang states' ultimate mission was to achieve political stability under the tianzi. This principle of politics, which had implications for the country's defence and security, is known in Chinese as siyi shuner tianxiazhu 《四夷顺而天下宁》 (four barbarians to obey, then the universe shall be peaceful). Indeed, the bestowment of gifts, permission to trade, blessings of official positions and other benefits served to neutralise the shubang states, which at times might be in a strong position to threaten China. This tactic, as claimed by Suebsaeng (1971), could meet the three objectives of China: first, to ensure temporary security through a policy of persuasion; second, to weaken less civilised countries by creating resistance through the notion of dividing and ruling the people within these states; and third, to establish ties with other powerful states or tribes. The tributary system reached its peak during the Song Dynasty in the 11 th and 12 th centuries, especially as it related to China's defence. During that time, the Song Dynasty had a weak military. Its demand for each nearby country, especially those in the China Sea, part of the western Pacific Ocean bordering the Asian mainland on the east-southeast, to bow to China was not based on its strength, but on the economic rights given to tributaries (Yu, 1967). As affirmed by Liang (1996) and Ford (2010), by creating good relations with neighbouring states, China would be able to spread its greatness and credibility to others who might acknowledge the country as shangguo and be willing to pay tribute to it. China would also be assured of an international environment of peace and harmony.
In line with the affirmation of its cultural superiority, China asserted that it was 'ideal that there should be only one political administration for civilised mankind and regarded its own as that government. Hence there was no pressing need to distinguish it from another' (Chaurasia, 2004, p. 2). In other words, China staked its claim as the superior power to its barbaric neighbours. There was thus a need for the latter to be treated as protectorates so that the progress of China's great civilisation could spill over to these backward states (shangfan), enabling them to become modernised (shufan). Confucius (511 BC-479 BC) stressed that foreign races should be assimilated into the civilisation and culture of China ('yidi jinyu zhongguo, ze zhongguo zhi' 《夷狄近于中国，则中国之》 (Cheng, 1964). As a result of their assimilation, these foreign countries would not threaten the security of China. In this way, cultural transformation served as a defence mechanism that protected China from foreign attacks. In Chinese, this is written as yi bu kou fu, yi bu luanhua《裔不谋复，夷不乱华》(The border people could not strategise the Middle Kingdom, nor could the barbarians cause disturbance among the Chinese (Zuo Zhuan [Zuozhuan Commentary]).
China also maintained that, as a tianzi (Son of Heaven), the emperor had the ultimate exemplar of virtue and patriarch of a China-centered family of nation. He was given a divine right to rule over all people but was expected to promote their best interest and not his own. Thus, China's policy on foreign relations should be based on the tributary system. Other countries should be willing to accept China as the suzerain to bring about the inflow of culture, with envoys from China enlightening them. As recorded in the Taiping Ji (Book of Taiping) in the year 976, as guimenguan, xinglu nan, shi ren qu, jiu bu hai (《鬼门 关，行路难，十人去，九不还》the archway of Guimeng Guan, difficult to pass; ten tried to cross, nine were attacked). The Guimen Guan is one of the traditional routes that connected China to Qinzhou, Qinzhou, Hepu, Hainan and Jiaozhi (Vietnam) (Yang, 2007). It was claimed that the Guimen Guan region was cursed, as travellers faced many difficulties, such as drought, infectious diseases, polluted water, and poisonous air (qi). However, Vietnamese envoys were determined to present their tribute, or gong, to the Emperor of China, regardless of the obstacles that came their way, because they yearned to be China's protectorate.

The Benefits and Implementation of the Tributary System
The protectorates could derive many benefits from forming a tributary relationship with China. Through this diplomatic connection, they were able to elevate their prestige and image, as they enjoyed the influence of China's civilisation and advanced culture as well as economic gains (Tsiang, 1935;Zhang, 2009Zhang, , 2015. They also reaped special privileges in trading activities through the tributary trade relations. For example, by insisting on such a relationship, Siam stood to gain many advantages, as reported by Viraphol (1977).
Foreign emissaries were given the opportunity to engage in trading activities while waiting to return home. They were also permitted to spend several days at a point on the border or a port determined by China. All the tribute-bearing envoys from protectorates, such as Vietnam and Japan, were allowed to trade at Beijing Huidong Guan for three or five days after receiving blessings. This is said to be the main reason for the continuity of the tributary system as the tributaries received trade remunerations (dao yi chaogong, buguo liyu shi《岛夷朝贡，不过利于市》) (Wenxian Tongkao [General History of Institutions and Critical Examination of Documents and Studies]).
Aside from the benefits of trading in China, it was thought that the protectorates were given equal gifts from the emperor when they presented tribute. However, Chun's (1968) analysis of the tributary trade between China and Korea reveals otherwise. In his research on the period from the reign of Emperor Zongde (1640) to Yongzhen (1728), he finds that the value of the tributary items from Korea was always higher, even though Korea requested to be exempted from sending tribute nine times within a period of 88 years. For its final tribute, Korea had to present items worth roughly 13 million liang, which far exceeded the requital from China. Based on this evidence, Chun (1968) refutes the notion that the economic terms favoured Korea, as alleged by many. Niu (1995Niu ( , 2003 reached the same conclusion after analysis of the number of tributary items from Vietnam to China. He believes that although Vietnam sent tribute less frequently and China's gifts increased in value, when the costs of delivery were considered, the value of items received by Vietnam was far lower than the costs of sending envoys to China. Despite its disadvantages, the practice of tributary-giving paved the way for trade activities between the two countries and the trade did occur on a larger scale. This form of trading was a kind of barter exchange between China and its protectorates (Li, 2004). So far, this paper has elucidated that the tributary system had two purposes: political and economic. However, research by Niu (1995Niu ( , 2003Niu ( , 2012 on the tributary relations between China and Vietnam shows that their interaction is more related to politics than economics, as China believed that as long as Vietnam continued to send tribute according to schedule, the amount of items given would not be a problem to China.
Generally, China placed great importance on the arrival of foreign emissaries; they were received with an elaborate ceremony incorporated into the tributary practice. The ritual of receiving these envoys was carried out exclusively under the supervision of the protocol and custom minister (Wang, 1965a(Wang, , 1965b(Wang, , 1968(Wang, , 1999(Wang, , 2005a(Wang, , 2005b. Another feature of tributary relations was the protection China extended to the protectorates. For example, in 1419, Megat Iskandar Syah (1414-1424) of the Malacca Sultanate notified Emperor Yongle (1403-1424) of the threats of attack from the Ayutthaya Empire (also known as Ayuthia or Ayudhya) in Siam. Emperor Yongle warned Siam not to attack, which caused the ruler of Siam, King Nakarintradhiraj (1409-1424), to cancel his plan to attack Malacca.
Diplomatic relationships with China were based on the principle of reciprocation and involved etiquette and rituals founded on Confucianism. Through this diplomatic submission, China's relations with the foreign countries were metaphorically likened to interactions within the family unit; China was portrayed as the father, while the protectorates were considered to be the children (Stuart-Fox, 2004). In China's view, presentation of tribute was an act of li, or a good deed that must be done with full ceremonial protocol. It was only after the customary ceremony honouring the emperor was completed that the ruler of a vassal state could validly sit on his throne.
China hoped that this tributary system based on Confucianism would transmit the culture and civilisation of China to its protectorates. By making them protectorates and culturalising them in accordance with Confucianism, it was hoped that all possible threats to China from these states would cease. The emperor was fully aware that his country was the 'wall' or protector of these states from the invasion of foreign parties, and this 'wall' could only be strengthened if they pledged their allegiance to him. China's sincerity was irrefutable, according to Wagar (1971, p. 37), as evidenced by the Chinese emperor's reference to Vietnam: Vietnam is one of our protectorates. Its governance mirrors the prosperity and sadness of our own family. Even if we could take advantage in politics, there exists the question of whether it will benefit them (Vietnamese) too. Are they really satisfied? Are they comfortable and do not feel the pressure of their responsibility to present tribute, attend royal audience and so on? Or do they feel insulted at their lower status and find excuses to free their country?
The emperor's limited power to intervene in the protectorates' affairs was explicit. His authority could be applied only within the Chinese territories, while the protectorates' affairs would come under the jurisdiction of their individual kings. Vassal states had absolute power over the internal concerns of their countries, despite the fact that in some areas, such as the pledging of loyalty, presenting of tribute and attending of royal audiences came under the purview of the Emperor of China. The regulations pertaining to their relationships clearly show that the Chinese emperor avoided meddling with the internal matters of his protectorates. Although the emperor was responsible for the continuity and independence of these vassals, China, as the 'father' in this international 'family unit', would not provide punishment or exert power unless it was necessary. According to Wade and Chin (2019), in a Chinese tributary model, an ideal ruler is one who treats people from within and outside of the country kindly, similar to the way in which a father treats his children. As an example, in the 1540s, Emperor Jiajing (r. 1521-1567) once reminded the ruler of Annam (Vietnam), 'I am the Emperor and I treat all under Heaven as my family' (Ming Shilu,. While he treated his vassals benevolently, the Chinese emperor would not fail to punish them when necessary; as Emperor Zhengtong (r. 1435-1449) once said, 'The court [China] does not anticipate and cannot bear to punish you [protectorates]' (Ming Shilu,. This implies that, at times, there was a compelling need to impose punishment to ensure the legitimacy of a newly formed government. The new ruler had to receive tianming in order to carry out his duty. This implies that when disputes in the protectorates arose, China would intervene only to punish a head of the state that had deviated from the rules and ethics of Confucianism, such as seizing control from a legitimate monarch on the throne. Fuma (2007) suggests that the reason why China sent punitive expeditions to Vietnam during the rule of Emperor Yongle, Emperor Jiajing and Emperor Qianlong was to fulfil the li (rites or propriety) and wenzui (chastisement) principles of Confucianism.
Meanwhile, the protectorates assumed that, if the Emperor of China recognised their sovereignty and legitimacy, they would be blessed with wellbeing and prosperity. The sending of tribute that followed recognition was a custom (li) that entailed a ceremony and fixed rules to ensure the survival of the system. As viewed by Rossabi (1983), Fairbank (1995 and Chang (2005), payment of tribute was a prerequisite for the protectorates to conduct trade with China, as this maintained and acknowledged its sovereignty and integrity.
The act of giving tribute in the context of this relationship was not for China's protection alone; it was also a symbol of the willingness of these states to accept and be a part of China's culture. It was not humiliating, but a blessing and symbol of appreciation. Historical records have proven that these protectorates were not only satisfied with the affiliation but also proud of it, and they had no intention to sever ties with the Emperor of China. For example, Vietnam had become more accustomed to the culture of China, especially after gaining its independence from China, and its influence was not only retained but also strengthened in Vietnam. As described by Jenkins (1979) and Woodside (1963Woodside ( , 1971, Vietnamese rulers continued to make their country a small replica of China. Among the nations that surrounded China, only Vietnam adopted the Mandarin system of administration, which linked the operation of the government to knowledge of Confucian classics. Confucianism is based on the idea of five categories of relationships with others (wulun《五伦》): relationships between the government and the people, between father and son, between husband and wife, among siblings and among friends (Shih, 2002). Overall, these ties are characterised by sanggang (《三纲》, three strong bonds), in which the younger members are lower in the hierarchy. They are required to abide by any instructions from the senior or dominant members (i.e. China). Members who are senior or dominant are required to be of good character and show concern for the welfare of those in the 'lower' ranks. Their behaviour should reflect the ethics of Confucianism; for example, when younger members break rules, senior members are responsible for teaching and punishing the latter (Wagar, 1971). On the international stage, Confucianism regards every person and country as a member of the family, although they may differ in terms of their status, age, power, and cultural advancement, particularly in the Far East. China was positioned as the member with unrivalled seniority in this Confucian family. States lower in the hierarchy depended on China, as the central figure. Thus, they paid respect to China, as their master. The status of a protectorate in this hierarchical network was not considered to be an embarrassment, but a benefit they would be able to attain a high level of civilisation after joining the 'family'. As noted by Cranmer-Byng (1973, p. 68), It was not simply that the Chinese regarded their culture as superior in a material and aesthetic sense; they believed it to be morally superior, and of universal validity. Though non-Chinese people were not forced to acknowledge and adopt Chinese ethical and social values, they were encouraged to do so and somewhat despised if they neglected the opportunity.
During his reign, Emperor Hongwu (1368-1398) of the Ming Dynasty emphasised the observance of customs and rites, which he believed to be a tool to govern and protect the defence of the country and a means to enhance human relations. It was written in Chinese as Li zhe, guozhi fangfan, rendao zhi jigang, chaoting suo dangxian wu, bu ke yi ri wu ye 《礼者，国之防范，人道之纪纲，朝廷 所当先务，不可一日无也。》) (Ming Taizu Shilu, 1418). As such, he believed that the practice of customs and rituals should be incorporated into the administrations of his vassal states. Additionally, they should play an important role in the tributary relationships between the emperor and feudal leaders, between feudal lords, between the central government and the governments of minor territories, between China and foreign countries and between the people of China and those outside of China. Initially, foreign relations during the era of the Zhou Dynasty revolved around Emperor Zhou as he was tianzi, the focus of all respect. As Confucius said, 'if the world has the way, then the rites, music and punitive attacks are all initiated by tianzi.' (tianxia you dao, ze li yue zhengfa, zi tyanzi chu 《 天下有道， 則 礼 乐 征 伐 ， 自 天 子 出 。 》 . However, since the beginning of the Spring and Autumn War period (403-221 BC), there was a shift of focus to the feudal leaders of different territories, depending on their supremacy over other lords (lile zhengfa zizhu houchu,《礼乐征伐，自诸侯出。》). This phenomenon was due to the existence of powerful feudal leaders, such as Wuba (《五霸》), and the governments of Qixiong (《七雄》). These territorial governments and leaders who gained victory over others established tributary relations with the outside world, perpetuating the rituals and customs as expounded by the Zhou emperor. They practised the same culture of seizing and controlling one another's territories.
Presenting a tribute to China involved a special and lengthy ceremony. The most important events celebrated in the palace were 'the three grand festivals', namely, the winter solstice, Chinese New Year and the birthday of the emperor. These events provided opportunities for tributaries to pay homage to the Chinese emperor as some tributary states or kingdoms only had to pay tribute once a year, or once every 10 years. For example, in 1723, when a Vietnamese tributary envoy was sent to China, he described feeling as if he were 'in the heavens as the sun and moon aligned vertically, in line with five celestial stars coming together' as she only had to pay tribute to China once every three years (Sun, 2005). Envoys were under close supervision, the number of people they travelled with, ships and escorts, the form of tribute and the schedule for presentation of the tribute were clearly specified for each state. For example, in 1663, China stipulated that Annam (Vietnam) should present its tribute once every three years. Meanwhile in year 1665, the Vietnamese envoys to the Chinese court had to use the passage from Taiping in the Guangxi Province (Qinding Da Qing Huidian Shili [Collected Statutes of the Qing Dynasty]).
In 1668, the number of tributary vessels from Vietnam was limited to no more than three, with each vessel having no more than a crew of 100. Upon arrival at Beijing, three high officials, escorted by not more than 20 other officials, were allowed to enter the palace (Kham Dinh Viet Su Thong Giam Cuong Muc [The Imperially Ordered Annotated Text Completely Reflecting the History of Viet]. During the Qing Dynasty, Vietnam sent 42 envoys to extend congratulations, request credentials, pledge loyalty to the king and seek information about a king's demise. Before the presentation ceremonies, the envoys were ushered into a hall to practise and internalise the protocol and etiquette that had to be followed. Later, after the envoys were received, they would be well treated with accommodations, transport, food and other necessities in addition to a variety of gifts. They would also be invited to attend royal banquets. Emperor Wudi (141-87 BC) of the Han Dynasty once entertained a group of four delegates from foreign countries with 'wine and meat dishes which are plentiful like the overflow of a lake' (jiuchi roulin,《酒池肉林，以飨四夷之客》) (Han Shu [History of Han Dynasty], Xiyu Zhuan [Western Region]).
These envoys were also required to perform the kowtow ritual (a bow of respect), which involved kneeling three times and bowing nine times, when in audience with the Emperor of China. The performance of this ritual symbolised their willingness to remain loyal and subservient to the emperor. However, there was a time when this ritual became an issue that provoked debate. In 1762, Vietnam's messengers bowed only five times instead of the requirement of nine times set by China. Subsequently, there was an outcry from Qing Dynasty because, in their opinion, Vietnam had not sufficiently demonstrated obedience and loyalty to their patron, China (Niu, 2005).
There were other regulations and specific conditions to which protectorates had to adhere. For instance, the title king or khan could be used only by the head of the protectorate. The title di (emperor,《帝》) gave the impression that the state was trying to release itself from the patronage of China, which would conflict with the teachings of Confucius, who once pointed out that 'in heaven there are no two sons, and among men there are no two kings' (tian wu er ri, min wu er wang, 《天無二日，民無二王》). However, the Vietnamese kingdom asserted that the world was divided into northern and southern domains, with each domain ruled by its own emperor. In their view, Vietnam's emperor was the rightful king in the southern domain, while the Emperor of China was the absolute king in the north. In other words, China and Vietnam should be considered as two different countries with the same status (Vuving, 2001).
Strangely, though there was disagreement over its status vis-à-vis China, the state of Vietnam resolutely modelled itself on the Chinese administration. The ruler of Vietnam often called himself 'emperor' in his dealings with states other than China. When appearing before China, he conceded to using the title vuong (king). According to Kang (2012), this proves that Vietnam not only submitted to the tributary system but also viewed itself as 'China's proxy'.
Over time, the terms of the tributary system changed, depending on the dynasty in power. In 1267, Emperor Kublai Khan (1215-1294) of the Yuan Dynasty (1271-1368) listed six conditions for establishing a tributary relationship with other states, while during the Qing Dynasty , there were nine rules to which protectorates had to abide (Qinding Daqing Huidian Shili). The conditions generally concerned the number of envoys, the period of time between tributes and audiences with the emperor, the number of items to be presented as tribute and the route that the envoys were required to use. However, in 1688, Emperor Kangxi (1654-1722) of the Qing Dynasty changed the frequency of tribute to once every six years (Qinding Daqing Huidian Shili). The frequency of tributes subsequently changed from every three years to every two years and then to every four years.

Concluding Remarks
The tributary system had been practised by China many years before the Ming Dynasty institutionalised it, creating rules and a defined system for foreign relations. During the Han Dynasty (206 BC-220 CE), this system was enhanced to ensure that protectorates were in a state of peace and harmony. China's wish was to harmonise and pacify, not to conquer or control other states. To China, 'everything was under the Heavens', but the world was divided into domains (China: guo, bang), and relations with other states were determined by a Confucian hierarchy involving China, the state that was most advanced, and surrounding states that were less civilised. In this world order, the centre (Zhongguo) represented civilisation (hua), while the surrounding states represented backwardness (yi). As a result, the centre's duty was to control surrounding states to achieve harmony. The world order was based on the understanding that a universal king had received a mandate from Heaven to rule overall. This concept of universal rule was probably adapted from the nomads of Inner Asia and then spread to societies across Southeast Asia. The offer of tribute was only symbolic because, from China's perspective, the moral value it represented was more important than the economic aspects of its foreign relations. Over time, changes to the regulations and requirements of the tributary system were necessary to adapt to prevailing developments in the region, such as the advance of the West. Particularly in the early 19th century, the encroachment of Western nations began to endanger the safety of China and its waters as the trade monopoly held by the Chinese court was broken up and private trading was introduced. These changes were also caused by the colonisation of protectorates by the West, especially in the early 20th century. Ultimately, these developments brought about the deterioration and eventual demise of the tributary system.