The American submarine campaign in the Pacific during World War II was a major contributor to the ultimate defeat of Japan. During the war, American submarines comprised less than two percent of the U.S. Navy, but sank almost 60 percent of the Japanese merchant marine and more than 30 percent of Japan's navy, including eight aircraft carriers.

Gato Leader moves the Leader series to Pacific waters, letting players lead a group of American submarines against the Empire of Japan. The core system of the game is built on U-Boat Leader and will be familiar to players of other Leader games, allowing them to get into the game quickly.