Mongols first invade Dai Viet

1257

A Mongol tumen rode south from Yunnan into northern Vietnam. Tran Thai Tong's forces evacuated Thang Long, waited for the summer heat and disease to ravage the invaders, then counterattacked and drove the survivors back across the border. The formula would be used twice more. The Vietnamese strategy of trading space for time, then exploiting climate and terrain, became a template for resistance that endured for centuries.