In the crucial period from 1978 to 1975, Japan jettisoned its "omnidirectional" foreign policy and embraced a closer and more integrated defense alliance with the United States. Concern about the Soviet threat was the chief motive for this shift. The deployment of Soviet troops in the Northern Territories (Southern Kuriles), the Soviet invasion of Afghanistan, and the deployment of Soviet Backfire bombers and SS-20 nuclear missiles in the Far East all provided impetus toward closer U.S.-Japanese defense cooperation. As Japan closely aligned its defense policy with the United States, Soviet-Japanese relations correspondingly deteriorated. Normal channels of communication were broken off. As the Japanese government elevated the Northern Territories issue to the forefront of Soviet-Japanese relations, Soviet criticism of Japan escalated. By the time Mikhail Gorbachev took power in 1985, Soviet-Japanese relations had sunk to their lowest point.