crusader

Short definition from Wiktionary

Noun

1. 1
   A fighter or participant in the medieval Crusades.
2. 2
   A person engaged in a crusade.
3. 3
   An American, especially a soldier or leader who wages war against Islamist militants.
4. 4
   A Westerner; a Christian, especially of European descent or a missionary.
5. 5
   (either attributively or in the plural) The United States and its Western allies.