The popularity of military saints increased with the preaching of the First Crusade in 1095; St Michael, leader of the heavenly host, St James the Moor-slayer and St George, whose appearance with St Demetrius at the siege of Antioch, fighting on the side of the Christians, perhaps assisted his eventual acceptance as patron not only of England, but also Portugal, Catalonia, Venice and Genoa.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.