Ioannes II achieved one of his greatest victories in Serbia. The Serbians had broken many treaties, and captured the fortress of Rason. The Byzantine commander of Rason, Kritop(ou)los, was punished for failure to stop the capture of the city by being paraded on a donkey in women's dress. Ioannes completely defeated the Serbs (whose military reputation was not high). He settled many prisoners in the area of Nikomedeia, adding to the army and to tax-registers