on 1 october 1941 "sisu", together with "nuoli", was patrolling east of gogland when it came across a large, stationary soviet minesweeper of the "fugas" class. "sisu" missed with her first torpedo, having mistaken the foam painted on the minesweeper's bow for an indication that it was actually moving. a second torpedo hit the minesweeper amidship and sank her.