A military reserve, active reserve, reserve formation, or simply reserve, is a group of military personnel or units that is initially not committed to a battle by its commander, so that it remains available to address unforeseen situations or exploit sudden opportunities. Such a force may be held back to defend against attack from other enemy forces, to be committed to the existing battle if the enemy exposes a vulnerability, or to serve as relief for troops already fighting. Some of the different categories of military reserves are: tactical reserve, operational reserve, and strategic reserve. A military reserve is different from a

military reserve force A military reserve force is a military organization whose members have military and civilian occupations. They are not normally kept under arms, and their main role is to be available when their military requires additional manpower. Reserve f ...

, which is a military organization composed of military personnel who maintain their military skills and readiness in a long-term part-time commitment to support their country if needed. Military reserve refers to specific trained pre-organized forces operating on an on-call basis from the main military force. Each member acts in combat as a regular soldier.

Reserves at various levels

In the modern battlefield, reserves exist at all levels, from a platoon held back from a company level engagement, to whole army

corps Corps (; plural ''corps'' ; from French , from the Latin "body") is a term used for several different kinds of organization. A military innovation by Napoleon I, the formation was first named as such in 1805. The size of a corps varies great ...

consisting of armoured and mechanised divisions which are held in reserve with the purpose of exploiting a breakthrough or containing an enemy advance. Typically what is a reserve for one

headquarters Headquarters (commonly referred to as HQ) denotes the location where most, if not all, of the important functions of an organization are coordinated. In the United States, the corporate headquarters represents the entity at the center or the to ...

is not the reserve for a higher headquarters (though depending on the setup they may be). So if one of a battalion's companies is held in reserve during a battle, the company is considered to be a reserve for the battalion but not for the brigade or the division, since it is committed to action in its parent battalion sector. Similarly the British Reserve Army of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

and the American Fifteenth Army of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

were only reserves in their theater, as far as the national Headquarters was concerned, they were committed since they were not available to be sent for action in any other theater.

Employment

Deciding when, where, and how to employ reserves is one of the most important choices a commander makes. Usually only a part of the reserves are utilised at any given time, since these are often sufficient to accomplish the task at hand. Committing the entire reserve at once - the "all reserves forward" order - is only considered in moments of extreme crisis, when it is clear the enemy will not be stopped otherwise. In the event of reserves being sent forward to exploit a breakthrough, some are typically held back to deal with a potential

counterattack A counterattack is a tactic employed in response to an attack, with the term originating in "war games". The general objective is to negate or thwart the advantage gained by the enemy during attack, while the specific objectives typically seek ...

. Reserves can also be employed to relieve troops in action, allowing those units to rest and regroup away from the front line. Reserves may also exist in a broader sense: instead of being designated as the reserve in one tactical area, units and formations may be held back as forces available for responding to new strategic situations, or for fighting a decisive battle, as the battleship ''

Yamato was originally the area around today's Sakurai City in Nara Prefecture of Japan, which became Yamato Province and by extension a name for the whole of Japan. Yamato is also the dynastic name of the ruling Imperial House of Japan. Japanese his ...

'' was.

Effect of reserves in history

Reserve troops—or lack thereof—have played a significant role in battles and campaigns throughout history, especially in the twentieth century. Nazi Germany deployed reserves from France and southern Europe to Tunisia, averting collapse in the wake of

Operation Torch Operation Torch (8 November 1942 – Run for Tunis, 16 November 1942) was an Allies of World War II, Allied invasion of French North Africa during the Second World War. Torch was a compromise operation that met the British objective of secu ...

, and later to Italy, assuming control over most of that country after the Allied landing and the Italian surrender. Conversely, the lack of reserves to deal with the Allied landings in Sicily compelled the Germans to shift forces away from the Eastern Front, hampering the 1943 Kursk offensive, and the expenditure of their last reserves in the

Battle of the Bulge The Battle of the Bulge, also known as the Ardennes Offensive, was the last major German offensive (military), offensive military campaign, campaign on the Western Front (World War II), Western Front during World War II. The battle lasted fr ...

contributed heavily to the general German collapse in 1945. In the aftermath of World War I, the extensive colonial commitments of the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

left few battalions available for the

Anglo-Irish War The Irish War of Independence () or Anglo-Irish War was a guerrilla war fought in Ireland from 1919 to 1921 between the Irish Republican Army (IRA, the army of the Irish Republic) and British forces: the British Army, along with the quasi-mil ...

, which hindered the British ability to deal with the crisis. At the

Battle of Gaugamela The Battle of Gaugamela (; grc, Γαυγάμηλα, translit=Gaugámela), also called the Battle of Arbela ( grc, Ἄρβηλα, translit=Árbela), took place in 331 BC between the forces of the Army of Macedon under Alexander the Great a ...

Alexander the Great Alexander III of Macedon ( grc, wikt:Ἀλέξανδρος, Ἀλέξανδρος, Alexandros; 20/21 July 356 BC – 10/11 June 323 BC), commonly known as Alexander the Great, was a king of the Ancient Greece, ancient Greek kingdom of Maced ...

held back his cavalry, using it first to deal with Persian flanking movements and later to exploit a gap in the enemy line and win the battle.

Example of reserves

There have been many examples of reserves formations throughout history.

British Reserve Army in World War I

The Reserve Army was a

field army A field army (or numbered army or simply army) is a military formation in many armed forces, composed of two or more corps and may be subordinate to an army group. Likewise, air armies are equivalent formation within some air forces, and with ...

of the British Expeditionary Force during the First World War. Under the command of

Lieutenant General Lieutenant general (Lt Gen, LTG and similar) is a three-star military rank (NATO code OF-8) used in many countries. The rank traces its origins to the Middle Ages, where the title of lieutenant general was held by the second-in-command on the ...

Sir

Hubert Gough General Sir Hubert de la Poer Gough ( ; 12 August 1870 – 18 March 1963) was a senior officer in the British Army in the First World War. A favourite of the British Commander-in-Chief, Field Marshal Sir Douglas Haig, he experienced a meteoric ...

, the Reserve Army was formed on 23 May 1916, prior to the

Battle of the Somme The Battle of the Somme ( French: Bataille de la Somme), also known as the Somme offensive, was a battle of the First World War fought by the armies of the British Empire and French Third Republic against the German Empire. It took place bet ...

, and was renamed the Fifth Army in October of that year. The intended purpose of the army was to carry out the breakthrough phase of the Somme offensive once General Sir Henry Rawlinson's Fourth Army had captured the German front-line trenches. For this role Gough was provided with the three British

cavalry Historically, cavalry (from the French word ''cavalerie'', itself derived from "cheval" meaning "horse") are soldiers or warriors who fight mounted on horseback. Cavalry were the most mobile of the combat arms, operating as light cavalry ...

divisions and in June he was allocated an infantry corps of three divisions to support the advance.

Strike Corps

Some armor heavy formations of India and Pakistan are designated as "strike corps" to take advantage of breakthroughs.

Reserves at various levels

Employment

Effect of reserves in history

Example of reserves

British Reserve Army in World War I

Strike Corps

See also

References

Further reading