The young monarch was supported by influential Chancellor Axel Oxenstierna, who in April 1612 agreed to prolong the truce with the Commonwealth until September 1616.

The fortress was defended by weak Polish–Lithuanian forces under the starosta of Rūjiena, Wolmar Farensbach, who capitulated after a two-day siege and joined the invaders.

The Hetman wanted to annex the entire Courland to Lithuania, but Sigismund III Vasa did not agree to this and left complete control over the duchy to Frederick Kettler.

Offended at the king, Radziwiłł resigned from the high command in Livonia and handed it over to Colonel Jan Siciński, who, with only 100 soldiers, moved to Estonia.

The Polish–Lithuanian side demanded the return of Pärnu,[3] but since the war between the Commonwealth and Muscovy continued, Sigismund argued successfully that the city would temporarily remain in Swedish hands.