Thieu.
After the US withdrew from Vietnam the Vietcong came into power. South Vietnam fell under communist rule by the Vietcong.
South Vietnam was considered an ally of the US.
Ngo ding diem
South Vietnam
The outcome of the war was the that invasion of South Vietnam by North Vietnam succeeded, and the US failed to prevent the unification of Vietnam into a single, communist country, which it has remained to this day.
USA lost to north Vietnam not south. The south was their ally.
With US/Allied aid, the South fought back. US Air Power BOMBED North Vietnam. US Navy warships SHELLED North Vietnam. South Vietnamese Air Force airplanes bombed and strafed in South Vietnam in support of ARVN/South Viet Marines/Rangers/etc. ground troops.
South (RVN-Republic of South Vietnam)
Strategic bombing was conducted over North Vietnam; tactical bombing was conducted in South Vietnam; Secret bombings were conducted in Laos and Cambodia.
The US and N.Vietnam agreed to a peace plan, but S. Vietnam rejected it, so it did not go through
North Vietnam started the war against South Vietnam; the US went to the aid of the South.
The US didn't invade South Vietnam. The Republic of South Vietnam asked for US help as they couldn't stem the Red Tide (communist infiltration).