On 19 April 1989, an explosion occurred within the Number Two 16-inch gun turret of the United States Navy battleship USS Iowa (BB-61) during a fleet exercise in the Caribbean Sea near Puerto Rico. The explosion in the center gun room killed 47 of the turret's crewmen and severely damaged the gun turret itself. Two major investigations were undertaken into the cause of the explosion, one by the U.S. Navy and then one by the Government Accountability Office (GAO) and Sandia National Laboratories. The investigations produced conflicting conclusions.

The first investigation into the explosion, conducted by the U.S. Navy, concluded that one of the gun turret crew members, Clayton Hartwig, who died in the explosion, had deliberately caused it. During the investigation, numerous leaks to the media, later attributed to U.S. Navy officers and investigators, implied that Hartwig and another sailor, Kendall Truitt, had engaged in a romantic relationship and that Hartwig had caused the explosion after their relationship had soured. However, in its report, the U.S. Navy concluded that the evidence did not show that Hartwig was homosexual but that he was suicidal and had caused the explosion with either an electronic or chemical detonator.

The victims' families, the media (CBS's 60 Minutes), and members of Congress were sharply critical of the U.S. Navy's findings. The U.S. Senate and U.S. House Armed Services Committees both held hearings to inquire into the Navy's investigation and later released reports disputing the U.S. Navy's conclusions. The Senate committee asked the GAO to review the U.S. Navy's investigation. To assist the GAO, Sandia National Laboratories provided a team of scientists to review the Navy's technical investigation. During its review, Sandia determined that the bags of powder used for the gun had likely been rammed farther into the gun breech and at a higher speed than designed (a so-called overram), resulting in the powder igniting while loading was still in progress. A subsequent test by the Navy confirmed that an overram could have caused an explosion. Sandia's technicians also found that the physical evidence did not support the U.S. Navy's theory that an electronic or chemical detonator had been used to initiate the explosion.

In response to the new findings, the U.S. Navy, with Sandia's assistance, reopened the investigation. In August 1991, Sandia and the GAO completed their reports, concluding that it was likely that the explosion was caused by an accidental overram of powder bags into the breech of the 16-inch gun. The U.S. Navy, however, disagreed with Sandia's opinion and concluded that the cause of the explosion could not be determined. The U.S. Navy expressed regret (but did not offer an apology) to Hartwig's family and closed its investigation.

A gun turret (or simply turret) is a mounting platform from which weapons can be fired that affords protection, visibility and ability to turn and aim. A modern gun turret is generally a rotatable weapon mount that houses the crew or mechanism of a projectile-firing weapon and at the same time lets the weapon be aimed and fired in some degree of azimuth and elevation (cone of fire).