1624–1626, seven medium size ships were built here, with tonnage ranging from 200 to 400 tons. They were manned mostly by local Kashubian fishermen, while marine infantry consisted of English mercenaries, employed by the Polish King since 1621. The biggest ship of the new fleet was the galleon Król Dawid commanded by James Murray. Second phase (1625–26) Before the end of the truce, Gustav Adolf initiated talks with Muscovy and the Ottoman Empire, hoping for a joint attack on Poland–Lithuania. Furthermore, he sent his envoys to Sich, trying to incite the Zaporozhian Cossacks, who were Polish subjects, to attack Turkey, and provoke another Polish–Ottoman war. On 27 June 1625 Gustav Adolf landed in Livonia with an army of 20,000. The main Swedish corps of almost 10,000 marched upwards the Daugava River, and besieged Koknese, capturing it after sixteen days. On 27 August the Swedes captured Tartu, and soon afterwards, Mitau. In early September 1625, Swedish forces invaded the Grand Duchy of Lithuania, capturing Biržai on 7 September. This success cut links between Polish–Lithuanian garrisons remaining in Livonia, and those stationed in Lithuania, as Sweden now controlled the line of the Daugava. Furthermore, on 27 September, Sweden captured the fortress of Bauska. Swedish successes were possible also because of a bitter conflict between two powerful Lithuanian hetmans, Krzysztof Radziwiłł and Lew Sapieha. As a result, the armed forces of both leaders did not unite and operated separately, which put the Commonwealth at a disadvantage. In October 1625 Radziwiłł retook several castles, while Sapieha fought off Swedish assault on Daugavpils. Radziwiłł then concentrated his forces in Courland, sending a few banners to harass Swedish units in Livonia. Meanwhile, Sapieha camped near Valle (Wallhof, southern Latvia), which lies halfway between Bauska and Koknese. Gustav Adolf was well aware of internal divisions among the Lithuanians, and decided to take advantage of it. On 13 January 1626 he concentrated his forces, and on 17 January 1626 the Battle of Wallhof took place, in which for the first time Swedish forces defeated the Commonwealth in open battle. At the Battle of Gniew, on 22 September and 29 September to 1 October 1626, the Swedish forces stopped three attacks by the hussars. Aftermath After this failure, the Lithuanians limited their activities to attacks on Swedish patrols. Gustav Adolf, on the other hand, was content with the performance of his army, and decided to transfer the war to