For 50 years, the United States has had ill-fated experiences in effectively fighting insurgencies. In counterinsurgency terms, Vietnam and Iraq form two legs of a historically fraught triangle-with El Salvador providing the connecting leg. In light of this history, the author analyzes where the United States has gone wrong in Iraq; what unique challenges the conflict presents to coalition forces deployed there; and what light both shed on future counterinsurgency planning, operations, and requirements.