In April 1978, a pro-Soviet government took control in Afghanistan and received economic assistance from Moscow.
After amin was assasinated the soviets replaced him by pro-Soviet Barbak kamal. The soviets stayed in afghanistan fot ten years fighting opponents of barbak kamal.
The soviet union invaded Afghanistan to protect its interests in a neighbouring state. The soviets saw the situation as something similar to hat happened in Czechoslovakia, however the Americans saw it as an attempt to spread communism.