World War II Gun Battery Unearthed at Ford Island

In March and April 2007, excavations for the installation of utility lines at the northern end of Ford Island uncovered the remains of a command center and two gun emplacements for 5-inch antiaircraft guns. These three structures comprised part of an anti-aircraft battery, the last of nine that were constructed following the December 7, 1941 invasion of Pearl Harbor, in anticipation of another attack. In four Historic American Engineering Record (HAER) reports, Mason Architects documented the current condition and described the original functions of the 1943 structures, and then they were buried again.

The HAER reports explain how the 5-inch guns and gun directories used in these batteries may have been salvaged from ships damaged or sunk during the December 7 attack – the USS California, USS Virginia, and even the USS Arizona.

The report also provides a detailed account of how the 5-inch guns could be accurately aimed and fired at incoming aircraft so that the shells would explode within lethal range of the target.

This process required

  • an operator to visually track a target;
  • the gun director, located in the command center, to estimate the target’s distance, speed, altitude, and direction and supply this data to an analog computer within the director;
  • the computer or rangekeeper in the director to calculate the future positions of the target, determine a firing solution (required gun elevation, training, and fuse and site settings), and send to the guns, via a fire control switchboard, aiming coordinates and settings for the time-fused projectiles; and
  • the operators of the guns to keep their controls continuously matched to the coordinates supplied by the director.

At the gun,

  • the fuse-setting crewman calibrated the time the rounds would spend in flight before exploding;
  • the shell man moved the round from the fuse-setting machine to the gun,
  • the trainer moved the gun from left to right,
  • the pointer moved it up or down,
  • and the sight-setter made sure that all indicators matched up before the gun was fired.

The 5-inch 25 caliber gun could hit targets at around 6000 feet; the 5-inch 38 caliber gun had double that range.

The batteries were initially manned by sailors from ships damaged in the December 7 attack.

The batteries, constructed by the Navy and the Army Corps of Engineers, included emplacements for the guns and shelters for the directors, ammunition, fire control, and generators. These were usually built of splinterproof reinforced concrete.

Fortunately, these gun batteries were never used.

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Photos: David Franzen; drawing: MAI; Historical photo: U.S. Naval Historical Center.

Site plan, showing the three structures and the distances between them.