So many historical mistakes Jonathan Drake. Crusades were originally called by Greek Emperor to fight Sultanate of Rum which they lost to it at the battle of Manzikert (1071), and they had problem to recapture the their territory back. Constantinople appealed to help to the West, which just recently was officially split between Catholic and Orthodox churches (1054). I Crusades war born. It not against the Ottoman empire as it did not exist as the state entity. Initial success boosted moral and several crusades were waged to either preserve or increase the size of the knight kingdoms in Levant. For the next 200 years, Crusades fought Byzantine Empire (1204), Ayyubids in Egypt, Suljuks in Syria, and so on. When Ottoman empire emerged from consolidation of territories in the Little Asia around 1300, Crusades were in history. Do not mix with Crusades against Ottomans who were invading Balkans in 15th century. Ottomans took large part of Europe until they were defeated in 1683 at Vienna. Ottomans depopulated large part of Hungary, Romania, and chunk of Poland during that time. In Czech Republic more than 100,000 were taken into the slavery in 1666. Countless cities from England to France to Italy were plundered by Ottomans and their population sold to slavery. Ottoman Empire was extremely cruel and one of the largest massacres in Central Europe before WWII occurred due Ottomans. Widespread slaughter of POW outside Vienna is one of them.