Poulsen led his dragoons once more at the outbreak of the 1658–1660 Dano-Swedish War, and integrated his company into the defence of Copenhagen. Poulsen himself was sent into occupied Zealand in order to organize a guerilla warfare resistance. On August 22, 1658, a decree ordered the peasants of Zealand to assist Poulsen in harassing the Swedish occupying forces. He assembled a company of "snaphane" militia within the month of August, though he lacked substantial support from the local populace. He led several successful charges against smaller Swedish contingents, but was finally forced to retreat. He returned to Copenhagen, and later rejoined the regular army. He was probably a part of the city defence during the Assault on Copenhagen in February 1659.