The People's Republic of China (PRC) conducted an amphibious assault on Hainan Island on 16 April, assisted by the Hainan communist movement which controlled much of the island's interior, while the Republic of China (ROC) controlled the coast; their forces were concentrated in the north near Haikou and were forced to retreat south after the landings.

Lines of communication between the branch and the CCP leadership were tenuous from the beginning, resulting in the Hainan communist movement developing independently and operating with minimal outside support.

The Hainan communists were nearly destroyed due to the confined geography of the island; like their mainland counterparts, the few survivors abandoned the urban coast for the rural interior.

[2][3] The communists and ROC created a Second United Front in response to Japanese aggression; formal arrangements for Hainan were only made in 1938 after the start of the Second Sino-Japanese War.

[4] The Hainan communists were further isolated by the Japanese invasion of the island in 1939[3] – they had little communication, and no radio contact, with the CCP leadership until the end of the war.

CCP orders to abandon the island in 1946 were rejected by the Hainan communists,[15] who spent the years following the Japanese withdrawal building popular support.

[16] By late 1949, the PRC was looking forward to finishing the war by capturing the islands constituting the ROC's remaining strongholds.

[18] In January 1950, Mao Zedong approved the invasion while in the Soviet Union for a state visit; he likely sought a victory to impress his hosts.

[21] Wang Guoxing and Ma Baishan travelled through ROC-held territory to communist-held Beijing in the fall of 1949; they were in the city for the proclamation of the People's Republic of China.

Ma relayed Feng's suggestion that the attack from the north be made of pincer movements rather than a frontal assault on – and battle of attrition for – Haikou.

The currency would be issued to invading PLA troops to purchase supplies on Hainan; the wider distribution and usage would help tie the island to the PRC's economy.

The HIC responded by issuing war bonds in the winter and spring of 1949–1950; this instigated a final suppression campaign by the ROC.

[30][31] The ROC bombed communist bases on Hainan and the Leizhou Peninsula with impunity; the latter had practically no anti-aircraft defences.

[34] Sanya and Yulin in the south fell to the communists within seven days of Haikou, allowing the PRC to proclaim victory on 1 May.

The assault across the strait was popularized into stories of a "people's flotilla" of wooden junks manned by volunteers and fishermen fighting metal ROC warships.