What is a stalemate and why did one develop on the Western Front?

A stalemate is a long period of stagnation in a war, in which neither side makes significant advances. The stalemate at Marne between the “Entente” (British and French) and German forces was due to their equal size and strength and to the use of new deadly weaponry, which drove each army to barricade themselves in trenches.

Explanation:

to fight against injustice and class division

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).