You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: LENIN 
Clue: For his subversive activities, Lenin was banished to this region in 1897
siberia

Category: WORLD HISTORY 
Clue: He completed vols. 2 & 3 of Karl Marx's "Das Kapital"
friedrich engels

Category: THEY DID GOOD 
Clue: He left the NFL's Arizona Cardinals to join the Army Rangers & was killed in Afghanistan in 2004

pat tillman