East Sea Campaign

The East Sea and Spratly Islands Campaign (Vietnamese: Chiến dịch Trường Sa và các đảo trên Biển Đông) was a naval operation which took place during the closing days of the Vietnam War in April 1975. The operation took place on Spratly Islands and other islands in the South China Sea (known in Vietnam as the East Sea). Even though it had no significant impact on the final outcome of the war, the capture of certain South Vietnamese-held Spratly Islands (Trường Sa), and other islands on the southeastern coast of Vietnam by the Vietnam People's Navy (VPN) and the Viet Cong (VC) helped the Socialist Republic of Vietnam assert its sovereignty over the various groups of islands after the reunification of the country in 1975. The North Vietnamese objective was to capture all the islands under the occupation of the Army of the Republic of Vietnam (ARVN), and it eventually ended in complete victory for the North Vietnamese.

In 1975, as units of the People's Army of Vietnam (PAVN) were pushing toward Saigon as part of the 1975 Spring Offensive, the North Vietnamese High Command decided to capture all South Vietnamese-occupied islands located on the southeastern coast of Vietnam, and in the South China Sea. Subsequently, different units of the VPN were deployed to coordinate their forces with local VC units in South Vietnam to take the Spratlys and other territories.

During the 1970s the Spratly islands was already a source of dispute for many countries in the region; Malaysia, the People's Republic of China (Communist China), the Republic of China (Taiwan), the Philippines and South Vietnam all claimed sovereignty over all or parts of the islands. In early 1975 the underlying tension between the claimants came to the surface when South Vietnam invaded Southwest Cay, then occupied by the military forces of its wartime ally, the Philippines. In order to lure the Philippines soldiers off Southwest Cay, it was reported that South Vietnamese authorities sent prostitutes to the birthday party of the Philippine military commander on another island.

While the Philippine soldiers left their post to attend the birthday party of their commanding officer, South Vietnamese soldiers moved in to occupy Southwest Cay. After the Philippines military realized they had lost their territory, they planned to retake the island from the South Vietnamese through military force. By the time the Philippines military were able to put their plan into action, the South Vietnamese had already built a strong defense on Southwest Cay, thus deterring any potential counter-attack. Later Southwest Cay would be the first major target for the VPN.

On 4 April 1975, the High Command of the VPN and the Command of Military Region 5, under the command of General Chu Huy Mân, agreed on a plan to seize some Spratlys and other groups of islands. Under their secret plan, the VPN deployed the 126th Battalion, a naval special forces unit of about 170 personnel, to join the VC 471st Battalion of Military Zone 5. They were supported by three transport ships, the T673, T674 and T675 along with 60 experienced sailors and technicians from the 125th Naval Transport Brigade. The operation would commence at 12.00 am on 9 April 1975, to coincide with the PAVN ground attack on Xuân Lộc and to take advantage of low tide to land the special forces on the South Vietnamese-occupied sections of the Spratly Islands. To maintain the secrecy of their operation, the VPN kept their radio communications to a minimum in the days leading up to the attack.

Unlike their North Vietnamese counterparts, South Vietnam possessed a large naval force with a strong fleet of ships. Hence the Republic of Vietnam Navy (RVN), commanded by Vice Admiral Chung Tấn Cang, were able to maintain a strong presence in the Spratly Islands, with only a handful of infantry units provided by the ARVN to protect the smaller islands surrounding the main Spratly Island. To defend the islands, ARVN forces were mainly equipped with small infantry weapons, as well as M-72 anti-tank weapons. Whenever necessary, the RVN could deploy the destroyer Trần Khánh Dư (HQ-04), the frigates Trần Nhật Duật (HQ-03), Lý Thường Kiệt (HQ-16) and RVNS Ngô Quyền (HQ-17), as well as the corvettes Ngọc Hồi (HQ-12) and Vạn Kiếp II (HQ-14) to provide fire support. The RVN also relied on two transport ships, namely the Lam Giang (HQ-402) and Hương Giang (HQ-403), to transport vital supplies and reinforcements to ARVN forces on the Spratly Islands.

On 9 April 1975, three VPN transport ships, disguised as fishing trawlers, began moving towards Southwest Cay in the Spratly Islands with members of the 126th and 471st Battalions all on board. On the morning of 11 April 1975, helicopters from the United States Seventh Fleet began circling the VPN transport ships, but they were allowed to move on as the disguised North Vietnamese 'fishing trawlers' were mistakenly identified as ships from Hong Kong. After the American helicopters flew away, the North Vietnamese continued sailing towards Southwest Cay. On the night of 13 April, the three ships were closing in on Southwest Cay from three different directions. During the early hours of 13 April 1975, personnel from the VPN 126th Battalion and the VC 471st Battalion landed on Southwest Cay using rubber boats.

Taken by complete surprise, the ARVN on Southwest Cay put up stiff resistance, but they surrendered to the VPN/VC after 30 minutes of fighting. The VPN/VC claimed to have killed 6 ARVN in action, and taken 33 prisoners. In response to the attack on Southwest Cay, the RVN immediately formed a task force which came in the form of the frigate RVNS Lý Thường Kiệt and the HQ-402 transport ship to retaliate, but both ships were forced to turn back and defend Namyit Island instead. Having achieved their initial objective, the VPN command sent out the transport ship T641, to carry all the captured ARVN soldiers back to Da Nang. With Southwest Cay firmly in their hands, the VPN command set their sights on the next three targets: Namyit, Sin Cowe and Sand Cay.