But the emperor rejected an outright invasion . Just coming off a disastrous Japanese campaign , the emperor was unwilling to commit the central government troops to what he considered a low priority affair . He was now focused on delivering the final blow against the Song ; the emperor ordered the Yunnan provincial army to secure the borderlands in order to block the escape path of the Song refugees . He also sanctioned a limited border war if Pagan contested the takeover . As planned , the Yunnan army proceeded to consolidate the borderlands in 1275 – 76 . ( Elsewhere , the main Mongol armies had captured most of the Song territory by 1276 . )