Historical Background

Battery Birkhimer is a historic coastal defense structure located at Diamond Head Crater on Oahu, Hawaii. Constructed in 1908, it was part of a larger series of fortifications built to protect Honolulu Harbor and Pearl Harbor from potential naval attacks. The battery is named after Brigadier General William E. Birkhimer, a U.S. Army officer who was influential in the development of coastal defenses.

Battery Birkhimer was equipped with three 12-inch mortars, designed to fire at enemy ships from long distances. These were part of the Fort Ruger military complex, which included several other batteries within Diamond Head Crater. Fort Ruger was established in the early 1900s as the first U.S. military installation in Hawaii, making Battery Birkhimer an essential part of the island’s early military infrastructure.

Battery Birkhimer remained in service during World War I and World War II, although its role diminished after World War II as newer military technologies, such as air power and missiles, made coastal artillery obsolete. In 1950, the mortars were decommissioned, and the site was no longer actively used for military purposes.

Location and Current Uses

The battery is situated on the inner slopes of Diamond Head, a popular area for both its scenic hikes and historical significance. Today, Battery Birkhimer is still part of the Fort Ruger military reservation, but it has been repurposed for civil defense and state operations. The underground areas of the battery now house the Hawaii Emergency Management Agency (HI-EMA), which is responsible for emergency preparedness and response for the state.

Accessibility

Because Battery Birkhimer is currently used by the Hawaii Emergency Management Agency, access to the interior of the battery is restricted to authorized personnel. However, visitors can still view portions of the exterior and gain insight into its historical significance through interpretive signs located in the surrounding area. The Diamond Head State Monument trail offers a broader experience of the crater, though it does not specifically include Battery Birkhimer in its main tourist route.

Obtaining Access for Historical Purposes

Access to Battery Birkhimer’s interior is not generally available to the public due to its current use for emergency management. However, those with a strong interest in military history, scholars, or organized historical tours may request special access for research or educational purposes. Inquiries can be made through the Hawaii Emergency Management Agency or the Hawaii Department of Land and Natural Resources (DLNR), which manages the Diamond Head area.

For those looking to explore military history on Oahu, alternative nearby sites, such as Battery Harlow or Battery Randolph (now part of the U.S. Army Museum at Fort DeRussy), are more accessible and offer detailed exhibits on coastal defense systems in Hawaii.

Sources

• Hawaii State Parks – Diamond Head link

• Historical Military Fortifications in Hawaii link