Gordon's War (1973)

They said it would take an army to get the mob out of Harlem. THIS IS THE ARMY! THIS IS GORDON'S WAR!

A black soldier comes home to Harlem after a tour in Vietnam and discovers that his wife had become a heroin addict and died of an overdose. Infuriated, he gathers three of his ex-GI buddies and they lay out plans to fight the drug dealers.