was Cham resistance that the Mongols decided to send a relieving
force overland through Vietnam. But again the Vietnamese objected.
This was not out of solidarity with the Cham, but because Mongol
conquest and occupation of Champa would have left Vietnam exposed
to attack on two fronts. The furious Mongol response came in 1285
when a Mongol-led Chinese force from Yunnan invaded Vietnam and
took Thang-long. As before, the Vietnamese mounted a sustained
guerrilla resistance under the inspired leadership of Tran Hung Dao,
and again heat and disease took their toll on the invaders. A Viet-
namese counterattack was successful. Remnants of the invading force,
retreating towards Yunnan, were ambushed in the mountains. Mean-
while an attempt by Sogetu to relieve the battered Mongol army ended
in his own death.
A second invasion was immediately ordered, this time from
Guangxi. A Mongol/Chinese army crossed into Vietnamese territory
in 1287 and, for the third time, seized the capital. But again the Viet-
namese resorted to guerrilla warfare. The Mongol cavalry was useless
on the Red River flood plain, and the Chinese infantry were again
ravaged by heat and disease. The following year, as the invaders ran
short of supplies, the Vietnamese won a great naval victory. Four
hundred Chinese junks were destroyed as they tried to manoeuvre in
shallow and confined Vietnamese coastal waters. The Mongol army
was again forced to retreat, suffering heavy losses on the way. Pru-
dently, both Champa and Vietnam thereupon dispatched lavish
tribute missions to the Yuan court to re-establish tributary relations,
though neither king attended in person.
So ended the Mongol attempt to extend their Chinese empire
into mainland Southeast Asia. Cambodia was never subject to the
same pressure. Having initially detained Khubilai’s envoys, the Cam-
bodian king, Jayavarman VIII, also sent tribute for fear that the
Mongol army in Champa might cross to the valley of the Mekong and
march south. Further west, the Tai/Khmer principality of Lopburi,
which had declared its independence from Angkor, sent its first tribute
A Short History of China and Southeast Asia