 After two unsuccessful attempts to find the Northeast Passage in 1609 and 1610, he caught the attention of King Christian IV.In 1612, during the Kalmar War (1611–1613), Jens Munk together with the nobleman Jørgen Daa led a successful attack on the Swedish fortress Älvsborg, near today's Gothenburg.In 1614, he led a search for the privateer Jan Mendoses, whom he fought in a battle at Kanin Nos near the entrance of the White Sea.