 In 1258, the Trần commenced regular diplomatic relations and a tributary relationship with the Mongol court, treating them as equals to the embattled Southern Song dynasty without renouncing their ties to the Song.According to Đại Việt historiography, they applied a scorched earth policy, burning all the farms and evacuating all food supplies around the capital, which starved off the Mongols.According to Đại Việt historiography, the Trần Emperor counterattacked at Đông Bộ Đầu, Thăng Long at midnight on 28 January 1258.