For us or for the French? The French definitely lost and although the US won every major battle, the American public at home lost the war for us. Probably the ones who lost the most are the Vietnamese people, who now live under socialist-communist control.

During WWII, the Japanese conquered French Indochina. France had been conquered by Germany, so the French did nothing to protect it. The USA, Russia, and China helped the Vietnamese defeat the Japanese and declare independence. Then, after the war was over, France decided that Vietnamese independence was a fraud and declared Vietnam to be French property again. Obviously, this caused a pretty serious misunderstanding between the Vietnamese and the French. Since France sucked at warfare, they begged the USA to go in and conquer Vietnam for them, and the USA shrugged and sent a few special forces to "investigate" or whatever. Meanwhile, Vietnam went to China to say "Hey, this isn't fair, we won our independence from the Japanese after the French abandoned us!" so the Chinese intervened and the war escalated. Eisenhower didn't want to get the US involved in an unwinnable war, so he refused to sent ground troops and North Vietnam formed as a Chinese-influenced state, and South Vietnam was left in opposition, as a haven for those who didn't want communism. But then, JFK was elected in the USA, and he wanted to attack communist countries (frankly), so he invaded Cuba and Vietnam and so forth, and all it did was cause a huge mess. The Vietnamese eventually came to resent the USA and united under communism after all. Americans got sick of the war, too, being that the USA had no real stake in it, and once Nixon was elected, he withdrew the troops and that was that.

North Vietnam. started it when they invaded South Vietnam. In Nov 1, 1955. https://www.google.com/search?q=November+1%2C+1955&rlz=1C1CHBF_enUS941US942&oq=November+1%2C+1955&aqs=chrome..69i57j0j0i20i263j0i22i30l7.1717j0j15&sourceid=chrome&ie=UTF-8 Vietnam was divided into North and South with the North being Communist headed by Ho Chi Minh and the South being non communist headed by Bao. Bao got overthrown by Diem who was really corrupt. His daughter won the national lottery twice. lol, Anyway, Ho invaded the south in 1955 and that was the beginning of the war. Its a very difficult question to answer with precision because so many different actors are involved. https://www.history.com/topics/vietnam-war/vietnam-war-history#section_2

It was their civil war. The north wanted communism, the south did not, so they fought over it. The USA got involved in our effort to stop the dreaded "domino effect" of communism taking over entire regions one nation at a time. Very similar to American involvement in Koreas civil war.