Terms & Concepts

Reserve Force

Written by: Masoumeh Abedini Translated by: Hadi Qorbanyar
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Reserve Force
Written by: Masoumeh Abedini

Translated by: Hadi Qorbanyar
A reserve force is a maneuver element held apart from the main assault echelon, typically positioned to the rear so it can be committed flexibly as the situation develops. In practical usage, the term reserve force has two distinct meanings. It may refer to a portion of a unit held back from the initial engagement—kept in the rear and uncommitted so it can be employed at a decisive moment. It can also denote service members who are not on active duty but remain trained and ready to be mobilized and deployed when required.

The reserve force is a key tool of command influence in operations. It is maintained to ensure flexibility, deal with unforeseen developments, and engage in at a decisive time and place.

Like the assault echelon, the reserve may also be organized with appropriate combat support and combat service support elements.

For a commander, the reserve is the single most important means of shaping the battle and making timely, effective decisions. It is used to sustain success, reinforce the main attack, and provide more security.

More often than not, deciding when, where, and under what conditions to deploy the reserve is the hardest and most critical decision a commander faces. At moments of crisis, all units must be engaged, and the reserve force must be committed without delay.

The reserve force gives a division the ability to regain the initiative through offensive action. Early in the planning phase, commanders determine the size, composition, and missions of the reserve based on mission requirements, the enemy, terrain, available forces, and time. Reserves give commanders the flexibility to capitalize on success or respond to emergencies and unexpected situations through offensive moves.

Depending on circumstances, the reserve force may be used for a variety of purposes, including taking advantage of the friendly fires or enemy weak points; launching an attack from a new direction against an enemy that has repelled the main assault; striking deep targets through flanking maneuvers; taking over the mission of an assault unit that has been forced to halt; clearing bypassed enemy elements or those that have ended up behind the main assault echelon; securing the flanks or rear of friendly forces; carrying out the decisive attack and securing the final objective; supporting adjacent units when required by the mission; maintaining contact with neighboring units (this is rare and usually done by only part of the reserve); reinforcing the main attack; holding the areas captured by the assault echelon.

The size of the reserve unit depends on available forces, the mission, and the overall situation. When attacking deep objectives—especially when intelligence on the enemy is limited, and the course of the operation is hard to visualize up to the final objective—a stronger reserve is required. Otherwise, a smaller reserve is usually sufficient. When both sides have roughly equal mobility, or when friendly forces enjoy superiority, greater emphasis is placed on maintaining a strong reserve force.

The reserve echelon can be employed in several ways, such as positioning near a road network to enable rapid commitment; moving behind the main attack; deploying where it can help secure command-and-control facilities; or situating in areas that provide maximum concealment from enemy observation.

In rapid operations, the reserve usually trails the assault echelon at a prescribed distance, whereas in slower operations it advances in successive bounds behind it. In some cases, reserves may be repositioned by army aviation. Regardless of how it moves, the reserve force must always be ready for rapid commitment, and its distance from the assault echelon should never exceed the effective range of supporting fires.

In a broader sense, the reserve force may consist of non-permanent military personnel and, at times, part-time or civilian elements organized within a military framework and mobilized for general defense against large-scale aggression. Maintaining such forces in peacetime helps reduce military costs while preserving readiness for war. In some countries, reserve service is compulsory, whereas in others, it is a part-time obligation.

One of the clearest examples of reserve employment during the Sacred Defense can be seen in Iraqi counterattacks, where Iraqi forces made effective use of their reserves to confront the Iranian troops. Iranian forces also relied on reserves when needed. During Operation Beit al-Muqaddas, for instance, the Nasr Headquarters was tasked with overseeing a particularly sensitive and complex axis of advance. After crossing the Karun River, units under this headquarters ran into serious difficulties. Some were halted by minefields and could not continue towards the bridgehead line. Nasr Headquarters ordered Nasr 3 to press forward more rapidly, secure the bridgehead, push towards the Arayez Canal, and relieve the pressure on Nasr 5. At the same time, Nasr 2 was instructed to speed up its advance west of Khorramshahr to encircle the city and cover Nasr 5’s right flank.

Due to poor coordination between Nasr 5 and Nasr 2, part of Nasr 2’s southern flank was left exposed, where the enemy units used to place heavy pressure on the Iranians. As a result, an infantry battalion from the 2nd Brigade of the 21st Division suffered severe casualties and found itself in a critical situation. In response, Nasr Headquarters committed its reserve force into the gap between Nasr 5 and Nasr 2. The reserve both sealed the breach and deployed a tank battalion on Nasr 2’s southern corner to support the depleted infantry battalion. In addition, artillery fire, Army aviation, and tank fire were used to reduce enemy pressure.^[1]

 

^[1] Daerat al-Maaref-e Defa Muqaddas (A Summery of the Encyclopedia of the Sacred Defense), Vol. 1, Tehran: Markaz-e Daerat al-Maaref-e Pazhuheshgah-e Olum va Maaref-e Defa Muqaddas, 1390, Pp. 347-349.