On 27 October 1981, a Whiskey-class submarine ("U 137") from the Soviet Union ran aground close to the naval base at Karlskrona in the southern part of the country. Research has never clearly established whether the submarine ended up on the shoals through a navigational mistake or if an enemy committed espionage against Swedish military potential. The incident triggered a diplomatic crisis between Sweden and the Soviet Union. Following the 1986 assassination of Olof Palme and with the end of the Cold War, Sweden has adopted a more traditional foreign policy approach. Nevertheless, the country remains active in peace keeping missions and maintains a considerable foreign aid budget.