Fort Ruger

Fort Ruger (1906-1959) - A U.S. Army Coastal Fort first established in 1906 on Oahu Island, Honolulu County, Hawaii. Named Fort Ruger in G.O. 15, 1909, after Major General Thomas H. Ruger, a Superintendent of the United States Military Academy who served in the U.S. Civil War and became a Major General at age 29. Abandoned in 1959.

Fort Ruger 1938 Aerial View (lower center)

Endicott Period (1890-1910)

Part of the Harbor Defense of Honolulu.

On 12 Aug 1898 Hawaii was formally annexed as an American Territory. Shortly thereafter U.S. engineers and troops arrived to establish the first U.S. garrison. The initial garrison was housed in a series of temporary camps until President Theodore Roosevelt established military reservations on 18 Jan 1906.

The Diamond Head Military Reservation was established on 27 Jan 1906 with an initial 720 acres that soon expanded to 755 acres. The reservation was renamed Fort Ruger On 28 Jan 1909 for Major General Thomas Howard Ruger.

Fort Ruger was built out as harbor defense fort for Honolulu Harbor with the cantonment outside the north side of the Diamond Head crater and coastal gun batteries in and around the crater. The first battery built was Battery Harlow with eight, 12" mortars. This battery was started in 1907 and completed in 1910 on the north slope of the crater. Four more smaller caliber batteries were begun in 1914 and another mortar battery was begun in 1915. The second mortar battery only housed four of the 12" mortars as was the practice for the newer mortar batteries.

The configuration of the batteries remained the same through World War I but the disarmament after the war saw four batteries deactivated (Battery S.C Mills, Battery Dode, Battery Hulings and the Unnamed Battery). In the 1930s two batteries were added, Battery Granger Adams and Battery 155 - Fort Ruger. Battery 155 - Fort Ruger was a battery of 155mm field mount guns on concrete Panama mounts located on the north side of the cantonment oriented more for land side defense than coastal protection.

After World War II began Battery 407 was started as a battery built into a tunnel in the side of Diamond Head Crater. Work on the battery was discontinued before completion at the end of the war in 1945 and it was never armed. In 1943 both mortar batteries were deactivate because they were obsolete and would be completely ineffective in any naval battle. At the end of the war only Battery Granger Adams was still active, it was deactivated in 1946.

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Fort Ruger 1922 Plan

Fort Ruger 1922 Main Post Plan

Current Status

Part of Diamond Head State Monument, Honolulu, Honolulu County, Hawaii.

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Location: Diamond Head State Monument, Honolulu, Honolulu County, Hawaii. Maps & Images Lat: 21.2675 Long: -157.808611 Multi Maps from ACME Maps from Bing Maps from Google Elevation: 200' at the parade, varies.

Sources:

• Roberts, Robert B., Encyclopedia of Historic Forts: The Military, Pioneer, and Trading Posts of the United States, Macmillan, New York, 1988, 10th printing, ISBN 0-02-926880-X, page 246
• Gaines, William C., A Military History of Diamond Head and Fort Ruger, Coast Defense Journal, Vol 19, Issue 2, Part 1, May 2005, pages 4-41
• Gaines, William C., A Military History of Diamond Head and Fort Ruger, Coast Defense Journal, Vol 19, Issue 3, Part 2, August 2005, pages 4-46
• Williford, Glen and McGovern, Terrance, Defenses of Pearl Harbor and Oahu 1907-50, Osprey Publishing, 2013, Print ISBN 9781849085723
• CDSG

Links:

• North American Forts - Fort Ruger
• Wikipedia - Fort Ruger
• Diamond Head Hike - Military History
• Hawaii State Parks - Diamond Head State Monument

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