As noted by envoys, several high-ranking noblemen fighting for Sigismund's cause were instantaneously sent to the scaffold. Further tensions and escalation of violence as well as Charles' unpredictable stance persuaded Sigismund to intervene. Christian IV of Denmark agreed to cooperate but would not join the armed conflict. The major seaports of Danzig (Gdańsk), Lübeck and Rostock were pressured to sever trade with Sweden. Polish privateers began to violently attack Swedish vessels in the Baltic. By February 1598 Sigismund assembled an army consisting of approximately 5,000 men. On 23 July 1598 the army left Danzig (Gdańsk) with 80 transports, several warships and exiled members of the Swedish parliament. Eight days later they landed in Kalmar, which surrendered without a fight.