Battle of Czarne The Battle of Czarne , also known as Battle of Hammerstein or Hamersztyn , took place during the Polish – Swedish War ( 1626 – 1629 ) , between April 12 and 17 , 1627 at Czarne ( Hammerstein ) , in the province of Royal Prussia , Poland . The Polish forces were led by Field Crown Hetman Stanisław Koniecpolski while the Swedes were led by Johann Streiff , Maximilian Teuffel ( Teufel ) and Johann Friedrich von Kötteritz . The battle ended with a Swedish surrender mainly due to low morale of the German mercenaries in Swedish service . These troops started a mutiny and negotiated with the Polish command without Streiff ' s knowledge and prepared to switch sides to join the Polish army . Being unable to trust their mercenaries the Swedish troops were forced to surrender . Background . In January 1627 Axel Oxenstierna developed a plan to destroy the Polish forces by flanking them from east and west . The western component was to come from new recruits in Germany ; their recruitment however was significantly delayed , and eventually ordered by Gustavus II Adolf to march for Poland before they reached the planned strength of 5 , 000 . They numbered about 1 , 000 reiter cavalry , 1 , 500 infantry and eight artillery pieces . Initially this put Polish forces under Field Crown Hetman Stanisław Koniecpolski in a difficult position , but eventually the German mercenary forces under Johann Streiff ( commanding the cavalry ) and Maximilian Teuffel were however separated from the main Swedish forces on March 20 , surprised by the flooding of the Vistula which made crossing the river impossible in most places . They considered retreating to Puck but Koniecpolski with 3 , 000 troops besieged it and the Swedes surrendered on April 2 before Streiff and Teuffel could arrive . Streiff and Teuffel decided to move towards Gniewno , through Czarne ( Hammerstein ) and Człuchów ( Schlochau ) . They reached Czarne around 10 or 11 April , but were surprised to realize then that the Polish forces of Koniecpolski were very close , in Człuchów . They attempted to break through Dobrzyń , but were repulsed by the Polish forces . Surrounded from most sides , and slightly reinforced by the rear guard under Johan Friedrich von Kötteritz , the Swedes begun fortifying their positions , preparing for a siege . Battle . At the time of the battle , the Swedes , not counting a unit under Kötteritz which garrisoned a nearby crossing at Gwda Wielka , numbered about 1 , 700 – 1 , 800 . Koniecpolski had only about 1 , 200 – 1 , 300 under his command , but ordered his units to advance on 12 April . The Swedish field fortifications were not finished , and Poles were able to break through the Swedish cavalry trying to protect them ; however , they were turned back by infantry fire . A second Polish attack that day , with infantry support , also did not manage to defeat the Swedes . By 13 April Polish reinforcements had arrived , giving Koniecpolski a slight numerical superiority . By 13 April the morale of the Swedish troops began weakening , and increasingly , there was talk about surrender . This began impacting the activity of Swedish troops , likely nullifying some planned raids outside their fortifications . Some negotiations begun on April 14 , but were futile , and another Polish assault on April 15 , while not fully successful , caused a mutiny in the Swedish camp , and eventually Streiff and Teuffel were arrested by their soldiers . Negotiation ensued , mostly concluded and signed on April 16 , with an official ceremony on August 17 . The Swedish infantry was to join the Polish army , the reiters were to swear never to fight against the Polish king , with volunteers also allowed to join the Polish army , and the Swedish loot from nearby lands was to be returned to the owners ( this caused some annoyance within the Polish army , whose soldiers preferred to continue fighting to take the loot for themselves ) . Eventually , about 500 reiters and 800 infantry joined the Polish army ; about 250 reiters left for the Polish borders . Aftermath . Koniecpolski then turned his army to advance against the main Swedish army of Axel Oxenstierna . The Polish victory , although only on a sideline of the major front of the war , had significant repercussions . It increased the morale of Poland and its allies ; motivating Gdańsk ( Danzig ) forces to advance towards Głowa , the Elector of Brandenburg to officially ally himself with Poland , Lithuania to renounce its own ceasefire with Sweden , and other foreign powers supporting Sweden at that time ( Ottomans and Russia ) to become less aggressive . With regard to the tactical situation , Koniecpolski managed to destroy most Swedish activity on the western bank of the Vistula , and limited their presence to only the eastern bank . He also reinforced his own army , preventing the Swedes from achieving the quick victory they desired .