Most torso wounds that killed Marines in Iraq might have been prevented or minimized by improved body armor, a Pentagon study found.

The unreleased study last summer by the Office of the Armed Forces Medical Examiner looked at 93 fatal wounds from the start of the war in March 2003 through June 2005. It concluded that 74 were bullet or shrapnel wounds to shoulders or areas of the torso not protected by ceramic armor plating.

The findings underscore the difficulty facing the Army and Marine Corps in providing the optimum level of body armor protection in a war against an insurgency whose tactics are constantly changing.

Both services have weighed the expected payoff in additional safety from extra protection against the measurable loss of combat effectiveness from too much armor.

"In response to the changing battlefield conditions and as new technologies emerge, the Army continues to develop improvements to soldier protection equipment to enhance survivability and mobility," Army spokesman Paul Boyce said Friday.

Boyce said he could not discuss details, but that U.S. soldiers' body armor is the best in the world.

"We take operational security very seriously and will not discuss in public sensitive issues that may render any insight to the enemy about our capabilities, fielding plans or tactics, techniques and procedures," he added.

According to a summary of the study obtained by The Associated Press, the 93 Marines who died from a primary lethal injury of the torso were among 401 Marines who died from combat injuries in Iraq between the start of the war and last June.

Autopsy reports and photographic records were analyzed to help the military determine possible body armor redesign. A military advocacy group, Soldiers for Truth, posted an article about the study on its Web site this week. On Friday evening, The New York Times reported in its online edition that the study for the first time shows the cost in lives lost from inadequate armor.

The study found that of 39 fatal torso wounds in which the bullet or shrapnel entered the Marine's body outside of the ceramic armor plate that protects the chest and back, 31 were close to the plate's edge.

"Either a larger plate or superior protection around the plate would have had the potential to alter the final outcome," the report concluded.