14th and 15th Century Crusades
Two subsequent attempts were made to rescue the Christian states.
The first, 1344, in which Clement VI, the Hospitallers, the King of Cyprus, and the Venetians were prominent, involved numerous leaders and countries, and continued with very little success until 1400.
The second, also a fruitless effort, 1443, after the Turkish Murad II had defeated the Greek emperor at Constantinople, 1422, and the Council of Florence had proclaimed a religious union of East and West, 1439, was brought to a close by the fall of Constantinople, 1453.
New Catholic Dictionary