The US Army Museum of Hawaii is housed in Battery Randolph, a "Coast Artillery battery" that was constructed in 1911 at Fort DeRussy. Designed to blend in with the surroundings, the battery featured two rifles that could "disappear" into the hillside (you will have to visit to learn how). It was one of sixteen such structures built by the Army Corps from 1906-1917 to defend Honolulu and Pearl Harbor. An attempt was made in the 1970s (?) to demolish the battery by wrecking ball, but the structure was indomitable and the contractor gave up. Instead, the structure was listed on the National Register of Historic Places in 1984.
The koa display cases were all constructed by retired cabinetmaker and WWII veteran cartographer Toshi Nakano, who grew up in Kapahulu (not far from this museum) and essentially volunteered his services.
Stepping into the battery takes you back to pre-contact Hawaii and the weaponry and major conflicts that developed from then to Vietnam. The exhibits are engaging, well-executed, and beautifully designed. You will also get to see how the battery was used and learn about decorated General and Kaua'i native Eric Shinseki and Governor George Ariyoshi, among many others.
Near the entrance to the museum is a not-to-be-missed gift shop and temporary exhibit area that currently houses an exhibit on the tremendous contribution Japanese Americans made to U.S. WWII efforts. This exhibit is a must-see for everyone, especially for locals. It pains me to think of the difficult position Japanese Americans endured as they were forced to reconcile their belief in democracy and love for Hawaii with the clarity of knowing the humanity of the "enemy". It is devastating to see how patriotic and committed Japanese American veterans were to the American cause while their families faced internment, outright discrimination, property confiscation, and years of difficulty and suffering that extended far beyond the war's end.
Overall the exhibit is very well done, but it was disappointing how the atomic bombings of Hiroshima and Nagasaki were glossed over. This is the only time in world history that atomic bombs were used. Neither this fact nor the resulting horrific aftermath and widespread long-term suffering of innocent civilians are acknowledged at all. Perhaps it is too painful, or too controversial, to address. Here is an interesting WashPo article on how this history of events is taught around the world.
On the second level of Battery Randolph, the U.S. Army Corps of Engineers exhibits several of their major projects in Hawaii at their Pacific Regional Visitor Center. Among them are Kaneohe-Kailua Dam near Ho'omaluhia Botanical Garden on the windward side of Oahu, Kawainui Marsh, and Kaumalapau Harbor on Lana'i. Highly recommend a visit here to anyone interested in learning about these projects, the USACE's work in Hawaii, or any young people with an interest in engineering, particularly coastal engineering.
Venturing to the second level will also take you to additional heavy weaponry, including a helicopter, and through the "Hot Air Flue", a ventilation corridor designed to release hot air build-up from interior power generators.
Comparing Battery Randolph to the Pearl Harbor attractions is an apples-to-oranges comparison. There is little overlap between what you will see at each, but they complement each other well. Pearl Harbor focuses largely on WWII. You tour memorials for the many that lost their lives during the 1941 Pearl Harbor attack and learn about "this day that will live in infamy", walk through a WWII submarine and hangars filled with vintage aircraft, learn about the significant role of the Battleship Missouri in WWII and other 20th century wars, and visit a museum filled with WWII-related artifacts. Battery Randolph has more in common with the National Memorial Cemetery of the Pacific in Punchbowl crater in that its coverage spans all Pacific-Rim wars.
You may leave here wanting to bring flowers to someone buried at Punchbowl. If you are so inclined but don't know anyone there, consider that there are many graves marked "Unknown" that on-site staff can help you locate during office hours.
This museum is located on the Diamond Head side of Hale Koa Hotel, not far from the 'ewa end of Waikiki. Three parking stalls right in front of the museum are reserved for the handicapped. Open 9 am - 4:15 pm, Tues.-Sat. (closed Sunday and Monday), and staffed by volunteers. Admission is FREE, open to the public, donations optional but appreciated.
You could be in and out in 30 minutes to an hour if you breeze through everything, but to really see it all will require several hours. The $5 audio tour is probably worthwhile.