The 1975 spring offensive (Vietnamese: chiến dịch mùa Xuân 1975), officially known as the general offensive and uprising of spring 1975 (Vietnamese: Tổng tiến công và nổi dậy mùa Xuân 1975), was the final North Vietnamese campaign of the Vietnam War that led to the capitulation of South Vietnam. In December 1974, People's Army of Vietnam's (PAVN) forces crossed from their bases in Cambodia and captured Phước Long Province by January 1975. After this success, the North Vietnamese leadership increased the scope of the PAVN offensive and attacked the Central Highlands from Cambodia in March, capturing the city of Buôn Ma Thuột on 18 March. These operations were intended to be preparatory to launching a general offensive in 1976.

Following these defeats, the South Vietnamese leadership realized they were no longer able to defend the entire country and ordered a strategic withdrawal from the Central Highlands. The retreat was a disaster as civilian refugees fled under fire alongside soldiers along a single highway to the coast. This situation was worsened by confusing orders, lack of command, and a well-led and aggressive enemy, which led to the destruction of most South Vietnamese forces in the Central Highlands. A similar collapse occurred in the northern provinces where PAVN forces captured both Huế and Đà Nẵng by the end of March.

Following the ARVN collapse, North Vietnam transferred its northern forces over 350 miles (560 km) south down the Ho Chi Minh trail through Laos and Cambodia to capture the South Vietnamese capital of Saigon and win the war in time to celebrate their late President Ho Chi Minh's birthday. South Vietnamese forces regrouped around the capital and defended the key transportation hubs at Phan Rang and Xuân Lộc, but the South Vietnamese had lost the political and military will to continue. On 21 April, South Vietnamese President Nguyễn Văn Thiệu resigned, hoping the North Vietnamese would reopen negotiations. However, the PAVN continued to attack. While IV Corps southwest of Saigon remained relatively stable, preventing VC units from capturing any provincial capitals, PAVN forces entered Saigon, forcing the South Vietnamese government, now under the leadership of Dương Văn Minh, to surrender on 30 April 1975.

The signing of the Paris Peace Accords in January 1973 did not end the fighting in South Vietnam since both sides violated the cease-fire and attempted to gain control of as much territory as possible. Occupation meant population control in any future negotiations or reunification effort. The fighting that erupted was not small in scale. The three-phase North Vietnamese "Land-grabbing-and population nibbling" campaign, for example, included four division-sized attacks to seize strategically advantageous positions. The International Commission of Control and Supervision (ICCS), established by a protocol of the Paris agreement, had been assigned the task of monitoring the implementation of the cease-fire. The principles of consultation and unanimity among the members, however, doomed any effort to control the situation or to stop cease-fire violations, and the ICCS ceased to function in any meaningful way within a few months of its establishment.

At the end of 1973, there was serious debate among the Hanoi leadership over future military policy as the Central Committee of the Communist Party of Vietnam convened to assess the progress of its efforts in the south. General Văn Tiến Dũng, PAVN chief of staff, and Defence Minister Võ Nguyên Giáp strongly urged the resumption of conventional military operations, warning that increasing passivity would affect the morale of the army. Premier Phạm Văn Đồng, however, feared resuming operations would drain vital resources needed for reconstruction in the north.

The final result of this debate was Resolution 21, which called for "strategic raids" on South Vietnamese forces in order to regain territory lost to the ARVN since the conclusion of the Peace Accords and to test the reaction of both the South Vietnamese military and the American government. The first blows of the new policy were delivered between March and November 1974, when the communists attacked ARVN forces in Quảng Đức Province and at Biên Hòa. Hanoi's leaders watched closely and anxiously as strikes by American B-52 Stratofortress bombers failed to materialize. During these operations, however, PAVN retook the military initiative, gaining experience in combined arms operations, depleting ARVN forces, causing them to expend large quantities of ammunition, and gaining avenues of approach and jump-off points for any new offensive.

South Vietnamese President Nguyễn Văn Thiệu had made his position on the cease-fire agreement quite public by proclaiming the "Four Nos": no negotiations with the communists; no communist political activities south of the Vietnamese Demilitarized Zone (DMZ); no coalition government; and no surrender of territory to the North Vietnamese or Provisional Revolutionary Government (PRG) – policies which all but abrogated the Paris Accords. Thiệu still believed the promise made by President Richard Nixon to reintroduce American air power to the conflict if any serious violations of the agreement took place. It was also assumed that U.S. financial and military aid would continue to be forthcoming at previous levels.^{[citation needed]}

On 1 July 1973, however, the U.S. Congress passed the Case–Church Amendment, legislation that all but prohibited any direct or indirect U.S. combat activities over or in Laos, Cambodia, and both Vietnams. On 7 November the legislative branch overrode Nixon's veto of the War Powers Act. During 1972–1973, South Vietnam had received $2.2 billion in U.S. assistance. In 1973–1974, that figure was slashed to $965 million, a more than 50 percent reduction. Nixon's growing political difficulties (especially the Watergate scandal) and the increasing antagonism between the legislative and executive branches over Vietnam policies, did little to dampen South Vietnamese expectations. Some among the Saigon leadership were more realistic in their appraisal. According to Republic of Vietnam Air Force (RVNAF) General Dong Van Khuyen: "Our leaders continued to believe in U.S. air intervention even after the U.S. Congress had expressly forbidden it ... They deluded themselves." The shock of reduced aid was compounded on 9 August, when Richard Nixon, the guarantor of South Vietnamese independence, was forced to resign from office. In October 1973, the Arab oil embargo began, and the resulting oil shock of 1973–74 caused a massive bout of inflation that largely destroyed the South Vietnamese economy with a spokesman for Thiệu admitting in a TV interview that the government was being "overwhelmed" by the inflation. One consequence of the inflation was the South Vietnamese government had increasing difficulty in paying its soldiers.^{[citation needed]}