thumb|[[Jack (flag)|Naval Jack of the Polish–Lithuanian Commonwealth Navy in the 17th century]]
Polish–Lithuanian Commonwealth Navy was the navy of the Polish–Lithuanian Commonwealth and existed from 1627 to 1643.
History
The Commonwealth Navy was small and played a relatively minor role in the history of the Commonwealth.
Despite having access to the Baltic Sea and temporarily to the Black Sea, neither Poland nor Lithuania had any significant navy until the first naval commission was established by Sigismund II Augustus during the Northern Seven Years' War in 1568.
Sigismund III Vasa's plans for fleet creation
thumb|[[Battle of Oliwa, 28 November 1627]]
thumb|upright|[[Dutch people|Dutch born Admiral Arend Dickmann commanded the Polish–Lithuanian fleet during the battle of Oliwa.]]
At the turn of the seventeenth century, Poland became ruled by the House of Vasa, and was involved in a series of wars with Sweden (see also dominium maris baltici). to make a Catholic Fleet with the mission to control the Baltic Sea from Aalborg, Kołobrzeg, Rostock, Friedrichstadt and Wismar (territories occupied by HRE's Admiral of the Baltic Sea, Albrecht von Wallenstein, ally of Spain) against the Protestant navies of Northern Europe, which were their common enemies at the time. This provocated a minor Polish intervention in the Thirty Years' War to help Spanish Netherlands against Denmark–Norway, England and Dutch Republic (planning to open a new front on the Eighty Years' War), in exchange for a promised Habsburg Spain's help against Sweden (agreeing that the Poles would then take over the Flanders navy and receive Spanish technical advice to their naval industry). The Polish ships, sent to Wismar, were much better equipped than the imperial ones, being Król Dawid their flagship, and even frightened Gustavus Adolphus of its potential if Wallenstein added his ships under construction or developed another separate Spanish Baltic Fleet, but some unforeseen problems arose as the Polish-Lithuanian crews refused to sail unless they were paid in advance, as many were river peasants (Kashubians and Flisacos of Vistula) who were used to plundering the coasts that the Swedes blocked, but the expedition to Wismar seemed useless and incomprehensible to them. Also, internal conflicts of interests and leadership between Spain, Holy Roman Emperor, Catholic League and Wallenstein, as the effects of the Spanish Bankrupt of 1627, prevented this Spanish-Polish fleet from having any relevant operations, being relegated to fighting the Danish and Swedish fleets in very small sporadic skirmishes, and their mission lost part of his proposal after Peace of Lübeck on 22 May 1629 (when Denmark quits from the War), as Spain wasn't really interested to fight against Swedes for Poland, just to divert the Dutch army in helping Danes in Germany while diverting forces at Belgium, and also get German ground military aid from Catholic League to fight in Netherlands or Italy against Dutch and France in exchange for Spanish support against Denmark (Spanish aid to Poland was conditioned on maintaining Danish conflict in Baltic Sea or avoiding Swedish intervention to Germany, so Austrian Habsburg would be free to help Spain by land). However, that Polish-Lithuanian fleet in Northern Germany provocated that Danes attacked Gdańsk and destroyed their naval industry on 1629, while the 10 Polish-Lithuanian ships on Spanish service were captured in 1632 during the Swedish intervention in the Thirty Years' War. Sigismund III and later Władysław IV, demanded compensation from Philip IV for some years for his lost fleet. Their main goal was to plague Swedish communication and supply lines near Piława (now Baltiysk in Kaliningrad Oblast) and on Zatoka Wiślana (Vistula Bay). There were plans to use Cossacks in their light but very fast boats against Inflanty (Livonia) and even to raid the Swedish shore (to burn, pillage, capture merchant ships etc.). Cossacks were known from their plundering raids on Black Sea (they even burned suburbs of Istanbul once or twice). Because of the overall tonnage and armament difference between Polish and Swedish naval fleets even before (in 1620s), the main role of the Polish fleet was to disrupt Swedish communication and supply lines, to capture merchant ships bringing supplies for the Swedes.
The king's plan never had strong support from Polish nobles (szlachta): high costs and reluctance to strengthen the king's power were always crippling Władysław's plans. Thus not even all the king's expenses for the modernization of those ten ships were fully repaid. Unfortunate international alliances (with Denmark and Muscovy) did not allow him to mount any offensive actions and the majority of the wars he participated in were defensive ones (like the Smolensk War with Muscovy in 1634). A new armistice with Sweden signed in Stumsdorf (Sztumska Wies) knocked the last argument out of the king's hand. After that the king wanted to use his ships to organize the first Polish merchant company (with help of Hewel), however Hewel's death stopped even those plans. Finally the ships were sold. The built fortifications were salt in Denmark's and the Danzig Patriciate eyes and under their pressure were destroyed in 1640s.
The Swedes were without king after the death of Gustavus Adolphus of Sweden and lost battles in Germany. The Polish nobles did not want to fight a new war so when the Swedes returned most of the lands they captured in the previous war, a new armistice for 35 years was signed. The cost of the Polish preparations for this war was comparable with the costs of the king's relief of Smolensk in 1634 and his campaign against Muscovy.
Commonwealth fleet after 1630s
The fleet was destroyed in 1637 by Denmark, without a declaration of war.
The remaining ships were sold in the years 1641–1643, which marked the end of the Commonwealth Navy.