in the shoulder by a Polish sniper, the Swedes decided to end the assault and withdrew from the field, reportedly in good order. Stanislaw Koniecpolski decided to take the war to the seas and gathered a small Polish–Lithuanian Commonwealth Navy of 9 ships, mostly with aid from the City of Danzig. He defeated a Swedish flotilla on 27 or 28 November 1627 (in the New Style calendar), at the battle of Oliwa near Danzig. Over the winter, Koniecpolski recognised the need to reform the Polish army, especially to strengthen the firepower of his infantry and artillery to match the Swedish units. The Swedes, for their part, learned from the Poles how to best employ their cavalry by using more aggressive tactics. 1628 In 1628 the Polish forces, lacking funding, were forced to stop their offensive and switch to defense. Swedish forces captured the towns of Nowy and Brodnica. Hetman Koniecpolski counterattacked by using his small forces most efficiently — fast cavalry melee attacks combined with the supporting fire of infantry and artillery, and using fortifications and terrain advantage. By that time the war had become a war of maneuver, with neither side willing to face the other without advantages of terrain or fortifications. It was a miserable year for Swedish occupying garrison troops, with epidemics wiping out huge numbers of men and horses. 1629 On 2 February, while King Gustavus Adolphus was wintering in Sweden and Hetman Koniecpolski was away in Warsaw, the Polish forces were badly defeated at Górzno, where a Swedish force under Field Marshal Herman Wrangel encountered a Polish army under Stanisław Potocki. The Poles suffered 700 dead and wounded plus 600 captured; the Swedes lost only 30 dead and 60 wounded. Hearing of the defeat, the Polish Sejm was persuaded to increase funds for the army and accepted military aid from the Holy Roman Empire in the form of a corps of imperial troops under Field Marshal Hans Georg von Arnim-Boitzenburg. Another imperial corps, commanded by Albrecht von Wallenstein, operated in nearby Pomerania. Nonetheless, Koniecpolski was forced to withdraw from several strategic strongholds in Polish Prussia: in time he managed to recapture the seaport of Putzig (now Puck). The Swedish king returned to Polish Prussia with substantial reinforcements in May, and marched south towards Graudenz (Grudziądz) hoping to cut-off Arnim's newly arrived imperial corps before it could join Koniecpolski. He was unsuccessful, and while withdrawing north