Almost 16,000 US service members have died since 2006, mostly in the United States

Some 15,851 U.S. active-duty personnel and mobilized reservists have died while serving in America's military since 2006 – but according to a new report, the biggest adversaries are not directly related to America’s involvement in global wars or deployment abroad.

According to “Recent Trends in Active-Duty Military Deaths,” conducted by the Congressional Research Service and made publicly available by the Federation of American Scientists, 72 percent of the total deaths – 11,341 – happened under circumstances outside of the battlefield, reinforcing the notion that military service comes with many perils even for those who never see combat.

The report, which was compiled with the use of data provided by the Defense Manpower Data Center and the service’s Casualty and Mortuary Affairs database, categorized the deaths under two main umbrellas: “Overseas Contingency Operations” (OCO) defined as military operations “in which members of the armed forces are or may become involved in military actions, operations, or hostilities against an enemy of the United States or against an opposing military forces,” and non-OCO.

“Approximately 11,341 service members have died in circumstances unrelated to OCO operations since 2006. On average, there have been 920 deaths each year,” the report stated. “Personnel perished in more than 70 countries (and at sea), with the majority 93 percent of deaths occurring in the United States.”

The data showed that the majority of service members whose deaths unfolded outside of OCO operations during this time period died “as a result of accident, self-inflicted wounds, or illness.”

“The data indicates a substantial percentage (14 percent) of non-OCO accidental deaths were related to substance abuse. Overall, alcohol or substance abuse played a role in 8 percent of all deaths,” the report continued.

Around 16 percent of all non-OCO deaths – some 1,807 – involved cars, trucks or other vehicles.

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In terms of OCO deaths, roughly 4,510 military personnel have died in more than 25 countries and locations at sea since 2006 – with improvised explosive devices (IEDs) attributed as having caused half these deaths in operational war zones.

Since 2006, around 2,177 U.S. troops were killed in Iraq – 1,756 in “hostile” circumstances and 421 in “non-hostile” circumstances.

“Half of these military deaths are attributable to IEDs which killed most U.S. personnel between 2006 and 2009,” the report explained. “Approximately 38 percent died under non-hostile conditions primarily from accidents including loss of aircraft or ground vehicle or as a result of self-inflicted injury.”

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Of the overall deaths in Iraq, 211 were classified as accidents, 151 as self-inflicted, 29 as illnesses or injuries, 24 as homicides and 6 undetermined. 1,082 were caused by IEDs and 674 were killed in action or died as a result of the wounds sustained.

U.S. soldiers prepare to raise the American flag during a memorial ceremony to commemorate the 16th anniversary of the 9/11 attacks, in Kabul, Afghanistan September 11, 2017. REUTERS/Mohammad Ismail - RC17AC996770

A ceremony marking a U.S. casualty in Afghanistan  (REUTERS, File)

And since 2006, 1,961 U.S. troops died in Afghanistan – 1,658 in “hostile” circumstances and 303 in “non-hostile” circumstances.

Almost half -- 47 percent -- were derived from IEDs, while the remaining “hostile” deaths were a result of gunshot wounds or other in-action physical traumas. A “substantial number” -- 162 --died in connection with the loss of an aircraft or ground vehicle – however, the report found that the majority of such incidents were classified as “accidental” -- 69 percent -- and occurred under non-hostile conditions.

Hollie McKay has been a FoxNews.com staff reporter since 2007. She has reported extensively from the Middle East on the rise and fall of terrorist groups such as ISIS in Iraq. Follow her on twitter at @holliesmckay