Loss-Exchange Ratio is a military term that calculates the comparative casualties suffered by each combatant

Combatant

A combatant is someone who takes a direct part in the hostilities of an armed conflict. If a combatant follows the law of war, then they are considered a privileged combatant, and upon capture they qualify as a prisoner of war under the Third Geneva Convention...

 from a battle, engagement or extended conflict. For example, at the Battle of Gettysburg

Battle of Gettysburg

The Battle of Gettysburg , was fought July 1–3, 1863, in and around the town of Gettysburg, Pennsylvania. The battle with the largest number of casualties in the American Civil War, it is often described as the war's turning point. Union Maj. Gen. George Gordon Meade's Army of the Potomac...

 (1863) during the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

, the Union

Union (American Civil War)

During the American Civil War, the Union was a name used to refer to the federal government of the United States, which was supported by the twenty free states and five border slave states. It was opposed by 11 southern slave states that had declared a secession to join together to form the...

 forces suffered approximately 23,000 casualties against 22,000 for the Confederacy

Confederate States of America

The Confederate States of America was a government set up from 1861 to 1865 by 11 Southern slave states of the United States of America that had declared their secession from the U.S...

 — a loss-exchange ratio of roughly 1:1. By way of contrast, at the Battle of Omdurman

Battle of Omdurman

At the Battle of Omdurman , an army commanded by the British Gen. Sir Herbert Kitchener defeated the army of Abdullah al-Taashi, the successor to the self-proclaimed Mahdi Muhammad Ahmad...

 (1898), the British/Egyptian lost around 482 men, while the Mahdist Sudan

Sudan

Sudan , officially the Republic of the Sudan , is a country in North Africa, sometimes considered part of the Middle East politically. It is bordered by Egypt to the north, the Red Sea to the northeast, Eritrea and Ethiopia to the east, South Sudan to the south, the Central African Republic to the...

ese lost about 27,700 — a LER of 57:1.

Historical applications

Loss exchange ratio has played a significant role in past wars, especially those that have devolved into stalemate

Stalemate

Stalemate is a situation in chess where the player whose turn it is to move is not in check but has no legal moves. A stalemate ends the game in a draw. Stalemate is covered in the rules of chess....

 and become wars of attrition

Attrition warfare

Attrition warfare is a military strategy in which a belligerent side attempts to win a war by wearing down its enemy to the point of collapse through continuous losses in personnel and matériel....

. For example, the German objective at the Battle of Verdun

Battle of Verdun

The Battle of Verdun was one of the major battles during the First World War on the Western Front. It was fought between the German and French armies, from 21 February – 18 December 1916, on hilly terrain north of the city of Verdun-sur-Meuse in north-eastern France...

 (1916) during World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 was not the seizure of any strategic objective, but rather to inflict an LER of 2:1 on the French forces and thereby cripple the French army.

During the First Indochina War

First Indochina War

The First Indochina War was fought in French Indochina from December 19, 1946, until August 1, 1954, between the French Union's French Far East...

, Vo Nguyen Giap

Vo Nguyen Giap

Võ Nguyên Giáp is a retired Vietnamese officer in the Vietnam People’s Army and a politician. He was a principal commander in two wars: the First Indochina War and the Vietnam War...

, the leader of the Viet Minh

Viet Minh

Việt Minh was a national independence coalition formed at Pac Bo on May 19, 1941. The Việt Minh initially formed to seek independence for Vietnam from the French Empire. When the Japanese occupation began, the Việt Minh opposed Japan with support from the United States and the Republic of China...

, told his French opposite number that "you can kill ten of my men for every one I kill of yours, and at that rate, I will still triumph." In fact, the LER was approximately 3:1 in favor of the French, and they did indeed withdraw in defeat. A total of 900,000+ North Vietnamese were either killed, wounded or captured during the First Indochina War.

Contemporary employment

It is arguable that the concept of the Loss exchange ratio has become relatively less important in modern Western military doctrine, as some military theories posit that it is just as militarily effective to disrupt enemy forces

Interdiction

Interdiction is a military term that refers to the act of delaying, disrupting, or destroying enemy forces or supplies en route to the battle area. A distinction is often made between strategic and tactical interdiction...

and outmaneuver them, thereby reducing their combat effectiveness without necessarily inflicting massive casualties.