In turning their attention to Southeast Asia, the Mongols
enjoyed a strategic advantage not available to most Chinese dynasties:
they did not fear attack on the empire’s northern frontiers. This may
not have been evident, however, to Southeast Asian rulers and their
advisers. Moreover, the failure of invasions of Burma and Vietnam to
secure their military objectives suggests two things: one is that despite
their formidable military might, the Mongols overreached themselves;
and the second is that they were entirely ignorant of conditions of
warfare in these countries, both in terms of climate and environment,
and with respect to the sustained opposition they were likely to
encounter.
Ruling elites in Southeast Asia probably drew other conclu-
sions. They had, after all, fought Chinese armies to a standstill, but
only after suffering terrible devastation. Moreover, successful defence
of territory was no guarantee that another invasion would not follow,
as it did for the Vietnamese. The best way to avoid that was to
acknowledge Chinese suzerainty and the superiority of the Son of
Heaven. The way to ensure security, in short, was to send a tribute
mission, and thereby participate in the Chinese world order. Investi-
ture might be as a vassal king of the Chinese emperor, but for
the royal courts of Southeast Asia this was recognition that also
reinforced political legitimacy.
One thing worth remarking on, in assessing the response of
Southeast Asian kingdoms to the Mongol threat, is the lack of con-
certed action. Apart from the brief alliance between the Tai kings of
Sukhothai, Lan Na and Phayao in response to the Mongol invasion
of Burma, the countries of mainland Southeast Asia did not conclude
any defensive pact or treaty. No attempt was made to form an anti-
Chinese coalition. A suggestion by Champa to conclude an alliance
with Dai Viet was rebuffed, and hatreds ran too deep between Champa
and Cambodia after a series of wars and the mutual sack of each others’
capitals. Ruling elites were indeed more likely to take advantage of the
predicament of other kingdoms than to come to their aid.
Mongol expansionism