CODEX: THE KOVENANT IMPERIAL ARMY.

Garrison Forces.

Once the students have graduated and have reached adulthood, then they are required to serve at least 2 to 3 years in the Garrison forces, with the option to stay in the garrison forces to recieve an even greater military training regime.
You see, the Garrison forces on each Kovenant world is not only to garrison the world as a standing army but also be a training and reserve unit.

Garrison forces are on every single Kovenant Imperial world and it is often where retired soldiers, those who managed to survive long enough would be reassigned after they have been retired in case this Veteran soldier were ever needed again and while there, they would help with the training of the newest batch of recruits.

It is a Garrison Force first and foremost, that also functions as Reserve as well as a training unit for future soldiers, giving its officers lots of potential training and learning experiences.

Yet, spite being a training and reservist unit, the Garrison forces are capable of forming armies when needed either to put down a rebellion, preserve the planetary government, overthrow the planetary government (Incase of the world in question rebelling) or protect the world againts enemy invasions, Alien or otherwise.

However, Imperial Garrison forces are typically motorised and not mechanised, as they were simply less of a priority when it came to the resupply and support of hundreads of thousands of different Imperial Army units fighting all across the stars. As such, Garrison forces are typically equipped with weapons and equipment from the remaining supply stores and thus, were typically given surplus equipment and supplies. Yet this was sufficient enough for their task as being Imperial Garrisons.

However, the type of formations fielded by Garrison armies are dependent upon the world in question, as while all garrisons would share the common similarities of having Infantry, Panzers, as well as Artillery and motorised elements, there are some worlds [I.E. Feral, Feudal, Death or Agri worlds] that field special types of Garrison formations depending on what the world has to offer...
One such example would be the inclusion of Mountain troops within the Garrison because of the world being littered with high mountain ranges, or the Garrison forces having an abundance of Motorised, or even outright Mechanised Infantry formations and even fully armoured Panzer Regiments, thanks to their garrisoned world being a highly industrialised one.

Typically, Imperial Garrisons can constitute entire armies of their very own and because they are tasked with the protection of an entire planet, Kovenant Garrison forces easily numbered into the tens of millions or even having a hundread Million men ready to be raised up in defence of a Kovenant World.
Supported by hundreads of thousands of Tanks, Artillery, and other types of military grade equipment in the tens of thousands. [Not including any Volkssturm militia forces]

The Minimum strength require for the planetary Garrison Force according to Imperial Army Regulations, was 15 to 55 Million Garrison troops, however this number was highly malleable and allowed for a high degree of versatility and this effectively allowed some worlds to modify the number of their local Garrison forces by as much as regulations allowed it or to expand it as necessary.
As such, in some planets, the Garrison forces could be as low as 13 Million Imperial Kovenant Garrison soldiers serving in its local plantery garrison forces.

In situations of dire emergency, Garrison armies on Kovenant planets could be swelled up to the Hundreds of Millions of soldiers and beyond, in order to aid in the war. Thus, allowing the Garrison to be able to hold its own ground until Imperial Reinforcements was to arrive.

However, as with any fighting force, this Garrison Forces, even if a single planet were to have 100 Million or more men ready to fight, will inevitably need war material and resources to fight.
As such, local Kovenant forces would make it a top priority to secure lines of supply, factories, manufacturing plants and other such locations from enemy attack, either from enemy air attacks or from the ground againts enemy soldiers.
However due to the often demanding nature of warfare, the army was more often than not, fighting a war on a planetary scale, which means that their forces are inevitably going to be stretched thin at some point in the whole battle line.