 It was only in the late 14th century that two relatively strong powers emerged in the Irrawaddy basin, restoring some semblance of normalcy.The vast region surrounding the Irrawaddy valley would continue to be made up of several small Tai-Shan states well into the 16th century.Perhaps the most enduring legacy of the Mongol invasions was the emergence of Tai-Shan states in mainland Southeast Asia.