On 12 May 1947, the autonomous region of West Kalimantan was established. It was led by Syarif Hamid II of Pontianak, who supported the Dutch endeavor to establish a federal United States of Indonesia (RUSI), of which West Kalimantan would be one component. Following the 5 April 1950 arrest of Sultan Hamid for complicity in a coup attempt against the RUSI government led by Royal Netherlands East Indies Army (KNIL) officer Raymond Westerling, there were demands from the public for a merger into the Republic of Indonesia, which took place on 22 April. On 15 August, The West Kalimantan autonomous region became part of Kalimantan Province, and two days later, the RUSI ceased to exist, and was replaced with a unitary Republic of Indonesia.