I have no idea why the Byzantines always do that, even when they are being overrun they have 3 stacks in Moldavia doing nothing. I wish somebody had an explanation for this behaviour.

Its true often the Egyptians can join the war on the Turks side, defeat the Byzantines then beat the Turks thus emerging as the power in the east, that can happen when the French are beating the English the HRE can jump in and together England and the HRE beat France.