Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

One failed strategy in this war was the Strategic Hamlet Program, and the Iron Triangle and Cu Chi were some of the extensive tunnels used by one side in this war. After this war, William Calley was convicted for his role in a massacre, and during it, a Buddhist monk immolated himself in protest of [*] Ngo Dinh Diem's policies. The My Lai massacre was perpetrated during this war, which saw the use of Agent Orange. The U.S. embassy was subjected to a surprise attack during this war's Tet Offensive, and America fully entered this conflict after the Gulf of Tonkin Resolution. For 10 points, name this proxy of the Cold War, after which Saigon was renamed Ho Chi Minh City.
History