The concept of suzerainty varied across time and places. I can give an idea of what it meant in medieval and colonial Southeast Asia (SEA), but even here it varied depending on where and when.

The concept of suzerain-vassal relationships was common in SEA. SEA polities tended to be organised along the “mandala” model, in which the ruler of a powerful principality would exert influence over the rulers of neighbouring principalities. These “lesser” rulers could comprise village chieftains or even other sultans and rajas who would pay tribute and supply goods and manpower when required, but otherwise pretty much run their own affairs. In return, the “main” ruler would reward these “followers” with annual gifts such as fine porcelain and cloth, or royal titles, and provide both supernatural and military protection. As the British colonial administrator J.M. Gullick wrote in 1958,

(The sultan) did not in most states of the nineteenth century embody any exceptional concentration of administrative authority. Powerful district chiefs could and sometimes did flout his wishes with impunity; some of them were wealthier than he was.

A sultan was generally in control of a royal district which he governed after the fashion of a district chief. But his role in the political system of the state, as distinct from his additional and local role of district chief of the royal district, did not consist in the exercise of preeminent power.

Vassals could be acquired through warfare - surrender or being conquered usually meant vassalage rather than assimilation or annihilation - but also through diplomatic endeavours, especially marriage alliances.

Loyalty was often to an individual, or, at most, a bloodline, rather than a state. If a ruler was deposed, the usurper could not count on the support of the vassals. When a ruler died, unless his successor had cultivated the relationships of the previous ruler, vassal states might break away.

Even when the ruler was alive, suzerainty had to be actively maintained. Take, for example, Sultan Agung (“Great Sultan”), who ruled Mataram, in Java, from 1613 to 1645. He was a talented commander who managed to conquer nearly the whole of Java, but trying to hang on to conquered territory was like playing whack-a-mole with vassalised sultans. Whenever he was occupied conquering new territory, freshly vassalised sultans behind the front lines would take the opportunity to rebel.

From what we know, it seems vassals would basically do whatever they felt they could get away with. In Timor, the Portuguese and Dutch jockeyed for control through vassalisation of local rulers. The Dutch signed agreements, and the Portuguese also required rulers to swear an oath of fealty, usually giving them a military title in return. Several rulers did both, and right up to the end of the 19th century, rulers would alternately hoist the Portuguese and Dutch flags depending on which suited them best at the time.

Because suzerainty rested on relationships, tradition and the suzerain’s power rather than formal treaty obligations, the most successful suzerains worked hard at maintaining their suzerain status. During the second half of the 19h century, for example, Siam exerted suzerainty over what are today the northern Peninsula Malaysian states of Kedah, Kelantan, Terangganu and Perlis. One of the Terengganu princesses became a minor wife of the Thai King Mongkut, while a consort of one of the Kedah sultans was a Thai. Mongkut’s successor, King Chulalongkorn, made frequent trips to the Malay tributary states. Malay dignitaries were encouraged to visit Bangkok and build close relationships with their Siamese counterparts. The sultans were consulted on several matters concerning them - in 1886, the Sultan of Kelantan made known his dislike for the traditional Siamese title for a retired ruler of Kelantan, as it had been bestowed on his estranged older brother. The Siamese king created another title specially for him.

This was no doubt a lot of work, but the alternative, which was outright annexation, was not always that straightforward. Siam, for example, conquered the Sultanate of Kedah in 1821, but after 20 years and 5 rebellions started to wonder whether it was quite worth it. The deposed Sultan of Kedah, meanwhile, decided that he was never going to get his throne back by force. In 1841 he was restored to the throne by mutual agreement, and in return he recognised Siam as his suzerain. As mentioned above, Siam had a much better relationship with Kedah, not to mention a much easier time, as its suzerain as opposed to its direct ruler.

Manpower obligations of SEA vassals

SEA had extremely low population density. The population density of maritime Southeast Asia in the 16th and 17th centuries is estimated to be a mere 3.7 per square kilometre. The population density for India in this period is seven times as large, for China and Japan over ten times as large. The prestige of a ruler often rested less on how much territory he controlled, and more on how much manpower he could muster. Thus, a common duty of a vassal state in SEA was to provide manpower.

If the victor of a war did not forcibly carry off people to his capital, one-off provision of manpower was often a condition of the peace and subsequent vassalisation of the loser. The Phongsawadan Yonok (the chronicle of the northern Thai city of Yonok) describes the result of a war with Burma in the 13th century as such:

Mangrai [the Northern-Thai King] led his army to Pagan state and camped on the Southeast. . . . The king [of Pagan] sent his mission with gifts for presentation to Mangrai to show his submission. Mangrai then asked him to provide two skillful gong-smiths and other smiths of skills requested.

Mangrai returned to [his capital] Muang Kumkhan, leaving gong-smiths [in his vassal states of] Chentung, Chiengsaen and other kinds of craftsmen at Kumkhan. The arts and crafts were then spread over the land of Lanna [Northern Thailand] until now.

The vassal often had to also provide an agreed upon amount of labour every year. The chronicles of Gowa, a sultanate on Sulawesi, describe how its vassals had to send labourers to its capital for specified duties, and how distant Timor had to send a tribute of 50 slaves a year.

There were also one-off demands for manpower - in times of war a suzerain might demand a certain number of warriors from each of his vassals, for example. Or if he was engaged in a particularly large public works project he might demand labour.

In return, the suzerain generally provided military protection for its vassal, although, as with the mafia’s “protection”, this was often from the suzerain himself.

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