After Indonesia proclaimed its independence on 17 August 1945, the entirety of Sumatra was declared a "de facto" part of the country. The central government established Teuku Muhammad Hasan as the island's first governor, and on 29 October 1945 Hasan selected Amir as the government representative in Langkat (later equated to regent), with his office at Binjai. Amir accepted the position readily, subsequently handling numerous tasks set by the central government, including inaugurating the first local division of the People's Safety Army ("Tentara Keamanan Rakjat"; the predecessor to the Indonesian Army) opening meetings of various local branches of national political parties, and promoting education – particularly Latin-alphabet literacy.