World of Warships is a free-to-play naval warfare-themed massively multiplayer online game produced by international game developer and publisher Wargaming. The game features aspects similar to World of Tanks and World of Warplanes, having several classes of warships fulfilling different roles within teamed player versus player battles. It was released for Microsoft Windows on September 17, 2015. The gameplay is team-based. There are four different classes of vessels: destroyers, cruisers, battleships, and aircraft carriers; these vessels span across ten tiers within the technology trees of several nations. Navies thus far represented include the United States Navy, Imperial Japanese Navy, the World War I and World War II navies of Germany, Royal Navy, the Tsar-era and Soviet-era navies of Russia, French Navy, and a Pan-Asian tree featuring ships from various East & Southeast Asian navies. Other navies so far in-game are represented with individual non-tree "premium" ships including the Polish Navy, Republic of China Navy & People's Liberation Army Navy (Both placed within Pan-Asia), Royal Australian Navy (Placed under the Commonwealth) and Regia Marina. Through research of each ship from each tier, a player can progress through the game. Each specific ship has a number of modules that can be accessed through experience. This experience is used to unlock modules, and when a ship's modules are completely researched, the player can continue to the next ship and the previous ship, if fully upgraded, becomes an Elite ship. Submarines are not present in World of Warships nor are there any foreseeable plans to implement in the game. .