This is a collaborative TL between B_Munro and I.
1300s:
The POD for this world comes in 1356, where, as OTL, after the Battle of Potiers, fremch King Jean II was captured. Like OTL, chaos ruled, with lords running rampant. However, in this timeline, The Black Prince exploited this chaos, taking Paris and becoming the major power in France. However, the English dream of ruling France was not fulfilled, though Brittanny was now under thir rule, they did not have the power to pacify the rest of France. So for the rest of the century, southern France was nominally English, but in actuality, a feuding group of statelets. Burgundy exploited this era by gaining influence in Eastern France, where they made allies, even vassals.
During this period, the Byzantine Empire, declining for centuries, saw itself lose more land to the rising Ottomans. Almost all land but Constantinople itself had been absorbed into the Ottoman domains. Still, the Ottomans expanded elsewhere, making inroads into Anatolia and fighting with the Serbians.