The Battle of Petropavlovsk was a land and sea military engagement fought November 4-7, 1926 during the Pacific War fought between the Allies and the Japanese for control of the Russian city of Petropavlovsk on the Kamchatka Peninsula. Occupied by the Japanese after the Battle of Bering Island in early 1925, Petropavlovsk became a crucial launchpad for Japanese attacks against the Aleutian Islands throughout 1925 and 1926 during the spring and summer months, and recapturing Petropavlovsk became a critical priority for the Allies following the repulsion of Japanese soldiers from the Aleutians in the summer of 1926.
The battle occurred during the early winter formation of sea ice in the Sea of Okhotsk and north Pacific, as the Japanese fleet was forced out of Petropavlovsk's harbor in order to remain in water. On October 24, Allied troops staged a massive landing on the southern shore of Karaginsky Bay and advanced down Kamchatka's central valley. On November 4, the agreed-upon date for the attack by Allied planners, the American Fourth Fleet and Alaskan Eighth Naval Group launched an attack on the Japanese Tenth Fleet IV Group, cornering the ships against the sea ice and staging the largest rout of a Japanese naval group in the entire war, with all eight ships sunk and close to 9,000 Japanese sailors killed. Later that afternoon, the Allied forces advancing through the central valley launched their attack on Petropavlovsk from the west while a second division of Alaskan soldiers was landed on coastal sea ice and crossed to assault the city from the northeast and east. The battle was an overwhelming victory for the Allies and was viewed as contributing to the lack of Japanese efforts to assault Aleutian-based supply routes for the next 10 months.
Many historians regard Petropavlovsk as one of the boldest tactical and strategic moves on the part of the Allies in the war and one of the biggest victories during the war effort.