During warfare, some units take more casualties than other units. Sometimes, the casualty rate is disproportionately high. This article displays the highest percentage of casualties among American units, including those wiped out as an effective force.

The term casualty in warfare can often be confusing. It often refers not to those that are killed on the battlefield but to those who can no longer fight. That can include disabled by injuries, disabled by psychological trauma, captured, deserted, or missing. A casualty is just a soldier who is no longer available for the immediate battle or campaign, the major consideration in combat. The number of casualties is simply the number of members of a unit who are not available for duty. For example, during the Seven Days Battles in the American Civil War (June 25 to July 1, 1862) there were 5,228 killed, 23,824 wounded and 7,007 missing or taken prisoner for a total of 36,059 casualties. The word casualty has been used in a military context since at least 1513.Oxford English Dictionary, Second Edition, gives a 1513 reference for military casualty, and an 1844 reference for civilian use.

Battles

UnitConflictDeploymentUnit sizeKIAWIAMIAPOWTotalCasualty rate (%)Opposing forceFate2nd Infantry RegimentSt. Clair's defeat(1 day of combat) 900 632 264 896 99.56Northwestern Confederacy inclu. Cherokee, Delaware and others Unit effectively destroyed, later replenished. A House of Representatives investigation was carried out to investigate the disaster, being the first Congressional Special Committee investigation.1st Minnesota Infantry RegimentBattle of Gettysburg, second day262 0 0215 82 ConfederacySurvivors reinforced by remaining companies of the regiment. Captured the 28th Virginia Colors at Picketts Charge the next day. Continued to serve in the Army of the Potomac until completion of enlistment on April 29, 1864. Majority of veterans formed the core of the new 1st Minnesota Volunteer Infantry Battalion.7th Cavalry RegimentBattle of the Little Bighorn 700~ 268 59 0 0327 45~ Combined Native American Army Arapaho tribe Cheyenne tribe Lakota tribes Unit effectively destroyed as a fighting force on 26 June 1876. Later replenished4th Marine RegimentBattle of Corregidor(2 days of combat) ~4,000 315 357 15 1,388 ~4,000Leatherneck Magazine, 4th Marines explore historic Philippine battle site, 1 February 2007. Nearly Total 4th Marine Regiment was destroyed only a few surviving Marines and personnel made up what was left of the regiment. The regiment was dissolved by Gen. Wainwright by his own will. Unit re-established in February 1944. 36th Infantry DivisionAttack across the Gari River(2 days of combat) 6,000 143 663 875 1,681 28.01 141st and 143rd Infantry Regiments destroyed as a fighting force. US Congress investigation to establish responsibility for the disaster in 1946.1st, 3rd and 4th Ranger BattalionBattle of Cisterna(1 day of combat) 767 311 450 761Zaloga S. (2005), p. 44 99 1st, 3rd and 4th Ranger Battalions destroyed.Cawthorne, Nigel, The Mammoth Book of Inside the Elite Forces, Robinson, 2008 1st Ranger Battalion reconstituted on 1 September 1948.3rd Ranger Battalion redesignated on 21 June 1954. 4th Ranger Battalion disbanded.1st Marine RegimentBattle of Peleliu(7 days of combat) ~3,000 1,749 58 Regiment relieved from combat, ineffective as a fighting force but not broken.28th Infantry DivisionBattle of Hürtgen Forest 16,266 6,184 38.0128th Infantry Division destroyed as a fighting force. Unit withdrawn for action. Later replentished.2nd Infantry DivisionBattle of the Ch'ongch'on River(4 days of combat) ~14,000 4,163 30 Major General Laurence B. Keiser commander of 2nd Infantry Division was relieved from command by the end of the battle.

US units with most casualties per conflict

UnitConflictDeploymentUnit sizeKIAWIAMIAPOWTotalCasualty rate (%)Opposing force1st Minnesota Volunteer InfantryAmerican Civil War 286 609 895 Confederacy1st Infantry DivisionWorld War I 4,964 17,2011,05623,221 German EmpireHarlem HellfightersWorld War I(191 days at the front) 3,832 1500 40~ German Empire3rd Infantry DivisionWorld War II(553 days of combat) 6,000 4,922 18,766 554 173525,977Army Battle Casualties and Nonbattle Deaths (Statistical and Accounting Branch, Office of the Adjutant General), 1 June 1953 Vichy France Italian Social Republic 1943–1945 1942–19431st Marine Division1st Marine Division was the unit with most casualties suffered during the Korean War with 29,868; including 4,004 KIA and 25,864 wounded. Regarding killed in action the 2nd Infantry Division was the unit with the highest ratio with 7,094 KIA and 16,575 wounded.Korean War1950-19534,00425,86429,8681st Cavalry DivisionStanton, Shelby, L., Anatomy of a Division: The 1st Cav in Vietnam, Presidio Press, CA (1987).1st Cavalry Division was the unit with most casualties suffered during the Vietnam War with 32,036; including 5,444 KIA and 26,592 wounded. Regarding killed in action the 1st Marine Division was the unit with the highest ratio with 7,012 KIA.Vietnam WarAug 1965 - Aug 1972 5,44426,59232,036 Viet Cong14th Quartermaster DetachmentThe 14th Quartermaster Detachment suffered the greatest number of casualties of any allied unit during Operation Desert Storm when an Iraqi Al Hussein Scud missile destroyed the installations the unit was located, after the failure in a Patriot air defense system that did not tracked the Iraqi missile location.Gulf War1990-1991691343005681.0 Iraq3rd Battalion, 5th MarinesWar in Afghanistan2001-201195025150175 18.4 Taliban

See also Deadliest single days of World War I List of battles with most United States military fatalities

Notes

References

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