The US military first established a presence on the Mokapu peninsula in the windward O‘ahu district of Koʻolaupoko in 1918, when President Woodrow Wilson signed an executive order establishing Fort Kuwaʻaohe Military Reservation on 322-acres on the northeast side of Mokapu. The army was responsible for the seacoast defense of Naval Air Station Kaneohe Bay, commissioned in 1939 on the Mokapu Peninsula. The Army stayed there until August 1940 when the Navy decided to acquire all of Mokapu Peninsula to expand Naval Air Station Kaneʻohe.
Following the December 7, 1941 attack, to defend the military facility at Mokapu, a number of gun batteries were built. In 1944, with two 8-inch guns, Battery 405 was built on the northeast lower slope of Puʻu Papaʻa, about 145- feet above sea level. The 542-foot peak is at the north terminus of the Oneawa Hills, on the dividing line between Kailua and Kaneʻohe. Following the war (August 27, 1946,) Battery 405 was named Battery DeMerritt, after Robert E DeMerritt, a Colonel with the Coast Artillery Corps during World War II. (The image shows a metal lath camouflage over an 8-inch gun to resemble a rooftop.)