Page "East–West Schism" Paragraph 53

In northern Europe, the Teutonic Knights, after their successes in the northern crusades, attempted to conquer also the Orthodox Russian Republics of Pskov and Novgorod, an enterprise endorsed by Pope Gregory IX.

One of the major defeats they suffered was the Battle of the Ice in 1242.

Sweden also undertook several campaigns against Orthodox Novgorod.

There were also conflicts between Catholic Poland and Orthodox Russia.

Such conflicts solidified the schism between East and West.