The second Battle of Guam began on July 21, 1944 with American troops landing on western side of the island after several weeks of pre-invasion bombardment by the U.S. Navy. After several weeks of heavy fighting, Japanese forces officially surrendered on August 10, 1944 was the American recapture of the Japanese-held island of Guam, a US territory in the Mariana Islands captured by the Japanese from the US in the 1941 First Battle of Guam during the Pacific campaign of World War II.
Liberation Day continues to be celebrated on Guam every 21 July.
On June 21, 1898, the United States captured Guam in a bloodless landing during the Spanish–American War. By the Treaty of Paris, Spain officially ceded the island to the United States. Guam became part of an American telegraph line to the Philippines, also ceded by the treaty; a way station for American ships traveling to and from there; and an important part of the United States.
Source: wikipedia.org | guam.gov