Following the development of the Cold War between the United States and Soviet Union, the government of Sweden adopted a stance of armed neutrality, seeking to avoid being pulled into the direct influence of either superpower.
To this end, Sweden maintained a sizable navy, and was concerned with interdicting any foreign forces that violated Swedish territorial waters in the Baltic Sea.
[3] During this same time, the Swedish parliament (having been reshuffled after a series of elections) was in a state of flux, effectively leaving the nation without a government from late September to early October.
[3][1] Once a decision was reached, Swedish forces began to hunt for the submarine; between 1 October and 14 October, numerous sonar contacts and purported sightings (including the detection of an oil slick) prompted the Swedish Navy to drop depth charges, deploy minesweepers, order increased naval patrols, and attempt to seal off Hårsfjärden Bay with a series of metal barriers.
[4][3][1][6][7] Other sources have speculated the submarine was present in Sweden during late September in order to track several American warships that were docked in Stockholm and to test the resolve of the then newly-elected Swedish parliament.