The Corps was perhaps the most useful and cohesive of the various high-level formations used by the Grand Army of the Republic and the Imperial Army—large enough to take most enemy worlds, it remained a key component in the armies of both the Clone Wars and the Galactic Civil War. It was also incorporated into the name of the Stormtrooper Corps.
Grand Army of the Republic
In the Clone Wars, a standard Army Corps consisted of four Legions of Clone troopers, 36,864 men in total; it was commanded by a Clone marshal commander and a Jedi General. Four Corps in turn formed a Sector Army.
However, a number of formations that would strictly be subordinate Legions within these Corps also used the term "Corps" in their designations. This may possibly reflect their growth into autonomous units of Corps size on their own, but at least some of them remained part of their parent Corps even when called "Corps" themselves—making it often very hard to know whether a unit was a Corps or a Legion in terms of its place in the hierarchy, or its number of troops. In practice, the situation was probably very fluid, with various legions in various stages of evolution, with extra troops, increasing autonomy from their parent Corps, and new Corps designations of their own.
One unit that was certainly a Corps was the 9th Assault Corps—because Commander Gree's 41st Elite Corps was one of its subordinate Legions. The 21st Nova Corps, the Galactic Marines led by Commander Bacara and Ki-Adi-Mundi, were also probably a Corps within the 4th Sector Army at some point in their existence, but the 327th Star Corps, led by Commander Bly and Jedi Master Aayla Secura, is officially a corps, as it includes the 7th Legion.
The Imperial Army was a much larger war machine than its predecessor had been, and composed largely of recruits from the civilian population rather than warrior clones. The white-armored elite troops who had been the backbone of the GAR had now been separated from the regular Army, and formed into a distinct arm known as the Stormtrooper Corps: as its name suggests, this was now organized as a single massive Corps, divided directly into component Legions, which could be assigned to Sector Group commands.
Within the rest of the Army, however, corps-level units retained a significance comparable to that which they had held during the Clone Wars. Many corps had their headquarters aboard a massive KDY-Evakmar military transport, which served to coordinate subordinate units on various planets and warships across the sector, and a barracks for troops in transit from one assignment to another. The same ship could also carry an entire Corps into orbit for a planetary-assault deployment; a single corps was regarded as a sufficient force to reconquer a planet that had recently thrown off Imperial rule, since it was expected for there to still be a significant Loyalist contingent and the Rebellion had not had the chance to reinforce their position. Typically the corps could expect to face odds of more than four to one, but regardless the Corps commander was expected to achieve local superiority and defeat the enemy in detail.
A typical corps in the Imperial Army was still divided into four multi-regiment tactical formations, but these were known as Battlegroups rather than Legions; and often, these Battlegroups were reorganized from Divisions which had been under planetary or sector command in the days of the Old Republic.
There were four standard types of corps - Line corps, Armor corps, Assault corps and elite Atrisian corps - and one corps of each type formed a standard Army. There was also the Corps HQs, which could function in an autonomous manner. A corps could also be augmented per their Order of Battle (OB), in which case the additional units were commanded by the corps' second-in-command.
There were three line, one assault and one auxiliary battlegroup in a line corps for a total of 48,541 troopers, 20,658 support personnel, 2,599 repulsorlift vehicles and at least 371 heavy tanks. It could be expanded with a mobile battlegroup, two more line battlegroups, and an armor battlegroup.
Named after the famous Atrisian Assault Corps of the planet Atrisia that inspired the politics of the Empire, the Atrisian corps were among the elite of the Empire. Essentially assault corps they contained two assault battlegroups, a line battlegroup, an armored battlegroup and an auxiliary battlegroup, giving them 48,403 troops, 3,385 repulsorlifts and 795 heavy tanks. Fully-expanded Atrisian corps added a mobile battlegroup, a third assault battlegroup, a second armor battlegroup and a second line battlegroup.
This corps was suited for operations where firepower was more needed than agility. Three armor battlegroups, a mobile battlegroup and an auxiliary battlegroup gave the armor corps a strength of 48,192 troops, 26,602 support personnel, 5,128 repulsorcraft and 1,219 heavy tanks. Augmentation could double the corps numbers with three more armor battlegroups and a second mobile
A mobile corps was the exact opposite of an armor corps: with its repulsorcraft vehicles the mobile corps could deliver fast strikes against rebel positions. Composed of three mobile, one armor and one auxiliary battlegroup, the mobile corps had a strength of 48,508 troops, 23,107 support personnel, 5,548 repulsorlift vehicles and 1,113 tanks. It could be augmented with three more mobile battlegroups and an assault battlegroup.
A Corps HQ of consisted a Major General and five staff officers (SP1-SP5), each of whom had two staff officers of their own (SP11-SP52), along with 388 support personnel, a security company of 156 troopers and six picket platoons under the command of major general or his second-in-command. The HQ was also burdened with three CompForce support platoons of 114 personnel total whose job was to support all CompForce units assigned to the corps, although their "support" was rarely adequate. Fifty ISB agents were also assigned to the corps HQ to ensure loyalty and provide intelligence, although it was the HQ's lone Imperial Intelligence agent who provided 15 to 20 percent of intelligence used by the corps. Finally the corps contained a huge number of droids, upwards of 2,000 in total from MSE-6 mouse droids to I2F-5 and I2F-73 industrial droids. These droids formed the basis of an impressive industrial complex which could transform even the most crude and basic materials into anything from blaster packs to repulsorlift engine. So long as the complex was operating the corps could operate indefinitely.
The corps HQ also formed the basis of the Imperial garrison of a world, which was why there were more corps HQs than there were corps in the Imperial Army (beyond being very pleasant assignments for very average major generals). These garrison HQs served as organizing points for rapid mobilization, and in a crisis quickly took command of units as they were transferred into the theater of operations. Under normal circumstances, much of the garrison commander's duties were taken up with representing Imperial authority on his planet, and thus there were often civilians agents associated with the corps HQ including diplomatic, medical, trade, scientific and technical personnel. While nominally outside the major general's command in reality these agents often operated under his orders.
The typical military contingent of these independent corps HQs was regimental in size, with four battalions of varying composition depending on the necessities of the situation. One popular configuration was a battalion of stormtroopers, two battalions of AT-ATs, and one of AT-STs. In addition the Ground Support Wing of an auxiliary battlegroup was always present, consisting of two TIE/gt squadrons, one TIE/sa bomber squadron and a TIE/fc spotter flight.
Behind the scenes
This balance of forces would have given the Corps HQ garrison an impressive combination of firepower, armor, reconnaissance, and maneuverability for its size. However, it is hard to conceive of the nearly 200 tanks and almost as many support vehicles of an armored brigade fitting inside the prefabricated garrison base that was the physical presence of a Corps HQ, and the another Rebel source, discussing the garrison base in detail, implies a deployment of just ten AT-ATs and ten AT-STs.
The same source suggests that a typical garrison's Ground Support Wing, nominally of 40 TIEs, comprised in practice three squadrons of whatever TIE Fighters were available, plus a flight of two TIE Bombers, with more bombers being added if the situation warranted them: this ties in with The Imperial Sourcebook's references to Army commanders having difficulty obtaining their correct compliment of TIEs, and adds weight to the evidence of this source's analysis.
Turning back to the armored units, the smaller figures can best be interpreted as representing a single armor company, with three tank platoons where The Imperial Sourcebook speaks of three battalions: two heavy platoons of five AT-ATs each, and one light platoon of nine AT-STs, plus a tenth AT-ST as a company command vehicle. It is unusual to find heavy and light armor mixed in this way, however, and it is possible that these armor platoons were designed as cores around which larger units could be formed as required: three battalions would form the basis of an armor regiment, and with this in mind, we can note the 40 speeder bikes cited as part of the garrison, which suggest the presence of a scout troop that could serve as the basis of an armor regiment's repulsorlift battalion.
- Imperial Sourcebook
- The Star Wars Sourcebook
- Imperial Sourcebook, Second Edition
- Star Wars Miniatures Battles Companion
- Guide to the Grand Army of the Republic
- Knights of the Old Republic Campaign Guide
- Star Wars: Imperial Handbook: A Commander's Guide