Who controlled the pacific in the beginning of WWII?

At the beginning of World War II, control of the Pacific was largely held by Japan. Following its aggressive expansion in the 1930s, Japan had established dominance over significant territories, including parts of China and various islands in the Pacific. The United States, while having a considerable naval presence, was initially focused on isolationism and was not fully prepared for conflict in the region until Japan's attack on Pearl Harbor in December 1941. This event marked a pivotal shift, leading the U.S. to actively engage in the Pacific theater.