After the Khmer Republic fell to the Khmer Rouge on 17 April 1975, a new regime under its charge, Democratic Kampuchea, was formed. Sihanouk was appointed as its Head of State, a ceremonial position. In September 1975, Sihanouk briefly returned to Cambodia to inter the ashes of his mother, before going abroad again to lobby for diplomatic recognition of Democratic Kampuchea. He returned on 31 December 1975 and presided over a meeting to endorse the constitution of Democratic Kampuchea. In February 1976, Khieu Samphan took him on a tour across the Cambodian countryside. Sihanouk was shocked to see the use of forced labour and population displacement carried out by the Khmer Rouge government, known as the Angkar. Following the tour, Sihanouk decided to resign as the Head of State. The Angkar initially rejected his resignation request, though they subsequently accepted it in mid-April 1976, retroactively backdating it to 2 April 1976.