The Republic of Vietnam (RVN) was a country that existed from 1955 to 1975. During this cold war period the RVN was a member of the Western Bloc.
It is bordered by the Democratic Republic of Vietnam (DRV) to the North, the South China Sea to the east and south, the Gulf of Thailand to the southwest, Cambodia and Laos to the West.

In 1945, when the Second World War was about to end, all colonial countries wanted to regain their independence. After the Japanese overthrew the French rule in Indochina on March 9, 1945, emperor Bao Dai invited scholar Tran Trong Kim to be Prime Minister, officially establishing the first cabinet of an independent Vietnam under the rule of law. Constitutional Monarchy.

On August 19, 1945, the Viet Minh Front (shortened term for Việt Nam Độc Lập Đồng Minh [Vietnamese Independent Allies], a political organization controlled by the Communist Party in the dark), seized power in Hanoi, pressuring emperor Bao Dai to abdicate. On August 25, 1945, not wanting a civil war, the emperor abdicated, giving power to the Viet Minh organization with Ho Chi Minh as president. He established a government, and made his national debut in Hanoi on September 2, 1945. He read the Declaration of Independence in Vietnamese, following the pattern of the 1776 US proclamation. Starting at the end of 1946, during the resistance war against France, the Communist Party of Vietnam eliminated the resistance elements of other parties and those with little prestige to monopolize.

As the outcome of the 1954 Geneva Conference, the territory of Vietnam was divided into two parts with the Ben Hai River (near the 17th parallel) as the border. North of the river is the DRV, under communism associated with China and Russia. South of the river are those who did not want to live under the communist regime.

Former emperor Bao Dai, as head of state, appointed Mr. Ngo Dinh Diem as Prime Minister. He assembled key people from the Vietnamese political parties and religions that are anti- communism to form his cabinet in Saigon on July 7, 1954. On October 23, 1955 Mr Ngo Dinh Diem organized a referendum and he won the election. On October 26, 1955 he proclaimed the creation the Republic of Vietnam and became its first president. “Vietnam is a Republic under the Presidential regime…, severed all ties with colonialism and feudalism, established an independent country in Southeast Asia and is part of the Free World. (1) page 719. Since then to April 1975, RVN was a free and democratic country. The capital is Saigon. The sovereignty of the Republic of Vietnam was recognized by 87 other countries around the world.

President Ngo Dinh Diem of the First Republic of Vietnam came to an end after a military coup in early November 1963, followed by a short succession of civilian and military governments. In 1967, General Nguyen Van Thieu won the presidential election. He won a second term in 1971. His presidency of the Second Republic of Vietnam ends on April 21, 1975 when he resigned.

The National Front for the Liberation of South Vietnam (Viet Cong) was established by Hanoi and officially launched at the end of 1960 in North Vietnam, with support mainly from China and the Soviet Union. During this period, the Viet Cong guerrillas joined forces with the North Vietnamese army to escalate the war in South Vietnam. The direct involvement of the US military with the Vietnam War immediately magnified the antiwar movement in the United States. Taking advantage of this situation, the North Vietnamese army rushed to turn the war into a battlefield, culminating in the Tet Offensive in early 1968, with two attacks on all cities, towns, and provincial capitals in South Vietnam, but they were defeated by the counterattack of ARVN units. However, it was also this event that made the United States think about withdrawing its troops from Vietnam.

During the first two years of the 1970s, when the rift between the Soviet Union and China escalated, the United States sought to improve foreign relations with China through Kissinger. They directly negotiated with the Vietnamese Communists in the North and forced the RVN to sign the Paris Peace Agreement of 1973. Key points of the agreement included a cease-fire throughout South Vietnam, the withdrawal of all U.S. troops and advisors and the dismantling of all U.S. bases within 60 days, the release all U.S. and other prisoners of war, the reunification of Vietnam carried out through peaceful means.

The United States withdrew all of its troops, but the North Vietnamese army and the army called the Liberation of the South were still present in the South Vietnam. In December 1974, they broke the cease-fire and attacked the south at Phuoc Long. They continued encroaching on South Vietnam territory with force until the end of April 1975. After the 1973 Paris Peace Agreement, the United States stopped military aid to the RVN, while Russia and China increased their aid to Hanoi. Thus, despite an armistice under the terms of the Paris Peace Agreement, communist forces invaded Saigon on April 30, 1975, marking the end of the RVN.

On July 2, 1976, the Provisional Revolutionary Government of South Vietnam (actually the Southern Liberation Front set up by Hanoi) and the Democratic Republic of Vietnam merged and become the Socialist Republic of Vietnam, as it is today.

Reference:
1) Việt Sử Toàn Thư by Phạm Văn Sơn, 1960.