Decrypting Mace Windu's Systems Army

The Grand Army of the Republic was a massive force led into battle by the Jedi Order.  Most members of the Jedi High Council were tasked with leading one of the Republic's ten systems armies as high generals.[1]  Unfortunately, most of the armies have not been thoroughly explored.  High General Mace Windu's Systems Army Alpha, however, is one of the most well-documented of these formations.[2]  This post will attempt to explore this army even further and resolve some of its unique issues.

The Second Sector Army

Each systems army was composed of two sector armies, each led by a senior general.[1]  One of Systems Army Alpha's component sector armies was the 2nd Sector Army.  This unit was led by Sr. Gen. Ry-Gaul and was further divided into four corps.  Only one of these units is known: Gen. Secura's 327th Star Corps.  The only known legion of the 327th was the 7th Legion.  Smaller formations are known,[2] but this article is more concerned with High Gen. Windu's unit as a whole, and less about the minutiae of the 327th Star Corps.

The Ninety-First Mobile Reconnaissance Corps

Another unit under High Gen. Windu, the 91st Mobile Reconnaissance Corps was far more confusing than its sister units.  The 91st was, at different times, led into battle by Mace Windu,[3] Adi Gallia[4] and Stass Allie.[5]  This would seem to be problematic, as all three Jedi were on the High Council, presumably making them all high generals.  This issue can be solved in three ways.

It's possible the 91st was transferred at least once between systems armies.  The corps could've started out under Systems Army Alpha, only to be moved to High Gen. Gallia's command later in the war.  Wether or not it was transferred again depends on if Stass Allie inherited Adi Gallia's command or not.  Since the two were cousins it's perfectly reasonable that Allie received Gallia's old systems army.

Alternatively, the 91st never actually changed hands.  Under this theory an instance of a contradictory leader would merely be the result of a temporary command.  However, we couldn't be certain who the 91st actually belonged to with this in mind.

Lastly, Gallia and Allie could have both been Windu's subordinates.  It may seem intuitive that all Council members were high generals, but this can't be the case.  The High Council contained 12 members while there were only 10 systems armies.  With two Jedi unaccounted for it would make the most sense for these Councilors to hold the second-highest rank.  Therefore, two High Council members would lead sector armies instead of systems armies.

Being one of the Order's most elite Jedi, it's certainly possible that another Councilor would be placed under Mace Windu's command.  Thus, Adi Gallia would lead the sector army containing the 91st under Windu's command (judging by the naming conventions, it would likely be the 1st Sector Army).  Eventually she would be replaced by Stass Allie.

The One-Eighty-Seventh Legion
One mysterious unit was the 187th Legion.  This unit served under High Gen. Windu, though we can't be sure where it was located in Systems Army Alpha.  This legion sported the exceptionally rare color of purple.[6]

One anonymous unit of purple-armored Clone Troopers served under General B'ink Utrila.[7]  Considering the tremendous amount of GAR units and the limited amount of colors visible to the human eye, it would make sense for each color to have clear associations.  Therefore, it would make sense for Gen. Utrila's troops to be in the same unit as the 187th, though we obviously can't be sure.

A Galactic Marine Regiment
The last mystery unit was a regiment of Galactic Marines, led by High Gen. Windu.  Next to nothing is known of these soldiers, but they sport nearly identical markings to the 187th.[8]  With the same paint job and leader it's very likely they were part of, or shared a common unit with, the 187th Legion.

It might seem like an issue, as the Galactic Marines were led by Ki-Adi Mundi.  However, Mundi's unit was officially known as the 21st Nova Corps.  "Galactic Marine" may be a more general term used by many different units.

Sources:
1. The Clone Wars Campaign Guide
2. Star Wars Insider 84 - Guide to the Grand Army of the Republic
3. Star Wars: The Clone Wars - Innocents of Ryloth
4. Star Wars: The Clone Wars – Nomad Droids
5. Star Wars: Episode III Revenge of the Sith
6. Star Wars Unleashed - 187th LEGION TROOPERS
7. The Clone Wars: Defenders of the Lost Temple
8. Order 66 - MACE WINDU & GALACTIC MARINE