 Disquieted by the Bulgarian attacks on Thessalonica, Michael switched sides and joined the Latins in defeating the Bulgarians at Pelagonia.It is commonly assumed that during these conflicts, Michael terminated his vassalage to the Latin Empire; historian Philip Van Tricht however points out that there are no sources for this, and that this vassalage may have survived until 1217, when Michael's brother Theodore captured Latin Emperor Peter II of Courtenay near Dyrrhachium.Sometime between 1210 and 1214, according to the "Chronicle of Galaxeidi", Michael came into conflict with the Latin Lord of Salona, Thomas I d'Autremencourt.