 According to the Soviet Politburo, they were complying with the 1978 "Treaty of Friendship, Cooperation and Good Neighborliness", and Amin had been "executed by a tribunal for his crimes" by the Afghan Revolutionary Central Committee.That committee then elected as head of government former Deputy Prime Minister Babrak Karmal, who had been demoted to the relatively insignificant post of ambassador to Czechoslovakia following the Khalq takeover, and announced that it had requested Soviet military assistance.Soviet ground forces, under the command of Marshal Sergei Sokolov, entered Afghanistan from the north on December 27.