 Complete the following phrase:  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 