Phase one of the Vietnam war: 1945 to 1954---Ho Chi Minh using the Viet Minh (a conglomoration of communist and other nationalist forces) fought the discredited French (the only French to rule in Viet Nam during WWII were the pro-Vichy forces who later were thrown over by the Japanese in 1945). Most of the fighting started in 1946. Defeat for the French at Dien Bien Phu by the Viet Minh under the command of General Giap. Geneva accord in 1954 with a military (but not political) division at the 17th parallel.
Phase 2: 1957 to 1975---Viet Minh in south renamed Viet Cong as a PR tactic by the American advisors. Big gains in the Mekong Delta by the Viet Cong. Corrupt Diem regime detested by most South Vietnamese overthrown with CIA help (and much acclaim by South Vietnamese) in November 1963. Soon Ngen Cao Ky ruled followed by Thieu (whose corrupt cousin raked in incredible amounts of booty). Unwinnable War of attrition thanx to McNamara. Tet offensive in 1968 finally broke the will of the American people and began calls for withdrawal.
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