He was subsequently besieged in Thebes and forced to surrender .
In the spring of 1258 , William marched on Thebes and defeated Guy in a hard - fought battle at the foot of Mount Karydi .
Guy was subsequently besieged in Thebes and forced to surrender .
In the spring of 1258 , William marched on Thebes and defeated Guy in a hard - fought battle at the foot of Mount Karydi .