The Battle of Arafura Sea (Indonesian: Pertempuran Laut Aru), also known as the Battle of Vlakke Hoek (Dutch: Slag bij Vlakke Hoek), was a naval battle in the Vlakke Hoek Bay (Etna Bay) of the Arafura Sea in Western New Guinea on January 15, 1962 between Indonesia and the Netherlands.
The battle stopped an attempt by the Indonesian Navy to drop off 150 soldiers in Kaimana in Dutch New Guinea for sabotage and to incite the local population against the Dutch government. Commodore Yos Sudarso was in charge of the operation at sea, while colonel Murshid commanded the infiltrants. Three Indonesian torpedo boats left the Aru Islands in the middle of the night but were intercepted near the New Guinea coast by a Dutch Neptune reconnaissance plane, as the Dutch had anticipated the action for weeks. The torpedo boats responded to the flares sent off by the plane by shooting at it. The Dutch destroyer HNLMS Evertsen then joined the scene and sank the KRI Matjan Tutul, commanded by Sudarso. The other two ships, KRI Matjan Kumbang and KRI Harimau, fled, but one hit a reef and the other was disabled by shooting. The Evertsen was able to save most occupants of the Matjan Tutul, but at least three sailors died, among whom was commodore Sudarso.
The Indonesian action itself was an abject failure and General Nasution even refused to relay the bad news to Sukarno, forcing colonel Murshid to do this in person. However, the small battle was partially responsible for the subsequent involvement of the Soviet Union and United States in the Western New Guinea dispute, and it is honored in Indonesia by "Ocean Duty Day" (Hari Dharma Samudera), an annual nationwide day of remembrance. Twelve years after his death, Yos Sudarso was officially added to the register of Indonesian heroes of the Revolution, while the KRI Harimau was made into a monument at the Purna Bhakti Pertiwi museum in Taman Mini Indonesia Indah.