When the
Torstenson War with
Sweden broke out in 1643, he was called in for duty with the fleet. In the beginning of 1644 he commanded a smaller squadron. After having joined forces in May with Admiral
Ove Gjedde at
Flækkerø (present-day island of Flekkerøy outside of
Kristiansand) they sailed together into the North Sea where on 25 May they fought an undecided action against a combined Swedish-
Dutch fleet under Dutch admiral
Marten Thijssen. Upon the return to Flakkerø, Mund accused several of his officers for having betrayed him to the enemy.{{cite web|url= http://www.jmarcussen.dk/historie/reference/person/gjedde.html {{cite web|url= https://sok.riksarkivet.se/Sbl/Presentation.aspx?id=5759|title= Mårten Anckarhielm|publisher= Svenskt biografiskt lexikon On 1 July 1644 he participated in the naval
Battle of Colberger Heide, as Quarter Admiral leading the 4th squadron. Again several of his ships' captains neglected their duties; at the very least, king
Christian IV complained loudly about them, writing that they had used him as a shield between themselves and the enemy. Whether this complaint was justified or not, it did not apply to Mund himself, who participated with great courage in the battle. His flagship
S:t Sophie appears to have suffered more casualties than any of the other ships. ==Death in the Fehmarn Belt==