Mordian Iron Guard

A planet of soldiers wearing Commissar-level hats. Let that sink in for a second. Note the Dredd pattern frown.

The Mordian Iron Guard are an army of the Imperial Guard, hailing from the planet of Mordian. They are renowned throughout the Imperium for being right hard bastards, never backing down and prepared to die to the last man as necessary.

They are also renowned for wearing spiffy dress uniforms, although they're not as classy as their equivalents in the Praetorian Guard.

Tactics

There are Imperial Guard regiments that rely on using well-planned strategies and combined arms tactics to overcome their foes. Then there are those that don't rely so much on strategy so much as throwing hordes of guardsmen into the fray, although said guardsmen are often some of the most badass motherfuckers in the entire galaxy.

The Mordian Iron Guard technically belong in the second category, but are so far around the curve that they start veering back into the first category. The first thing to consider is that they hail from Mordia, a world that actually has two classifications; half Death world, half Hiveworld. Absorb this for a moment while We get the Mechanicus to manufacture Balls big enough to comprehend this. Normally these two types of worlds are mutually exclusive, for a world itself trying to Kill you would put a lot of people off the concept of actually erecting massive towering cities on it. Not so for the Mordians. The planet spins at the same speed it revolves, so one side of the planet is constantly bleach-roasted by the Mordian sun, and the other side lives in zero degree dick-freezing perpetual night, much like how our Moon has one side always facing Earth. The Hive Cities are built on the night part. Thus every Mordian native is also a hiver, with years of experience ducking and kill inside narrow corridors where hive gangs exist on every level and crime is rampant in the places where the sun-don't-shine (i.e. the entire side of that planet). It got so bad that up until recently there was a notorious chaos uprising and the Mordians had to fight tooth and nail just to keep their inhospitable half of the planet from being overrun. The result is an established army that practices iron hard discipline (hence their name) and constant regimental routine. Nearly every citizen on Mordia has served in the planet's military, as it was the only way to maintain global discipline. 'we don't have enough personnel to police the entire damn planet so we're just going to conscript the whole population and have you all police yourselves'.

Consequently, Commissars find a tour on Mordia as rather boring, and a little intimidating as the Mordians themselves will penalize Commissars that falter in their duties. Again, absorb this for a moment. In every other part of the Imperium, Commissar shoots you for lack of discipline. On Mordia, You shoot the Commissar for lack of discipline. This is then reflected in their form of battle tactics. Rather than ride Chimeras or wear camouflage, Mordian guardsmen march into battle in brightly-coloured cloth uniforms and bearing equally flashy banners. They then form up into neat firing lines or squares and shoot at their enemies in disciplined volleys. They don't break formation, they don't take cover and they never, ever retreat. While this is incredibly ballsy even by Imperial Guard balls-of-steel standards, it is also incredibly stupid because on the battlefields of the 41st millennium there are oh-so-many ways to wipe out massed formations of infantry out in the open. These sorts of tactics were on their way out in the US Civil War when caplock minie ball rifles and rifled cannons began to appear. Even Space Marines will take cover whenever they can. But, somehow, the Mordians still survive their battles and keep going. Considering the horrors the Imperial Guard fights, you have to wonder how their training conditioned them so well. Then again, maybe you don't want to know.

Although a few sources note that this baffling lack of common sense causes their adversaries to underestimate them, it still doesn't really make up for employing infantry tactics that have long been redundant. That being said, the Mordians do have a few tricks up their sleeves, like flak and carapace armour actually sown into their rigid uniforms (which makes it both elegant AND protective), as well as having heavy armour companies with over a dozen Baneblades each. They also have 'veteran' companies who wear the incredibly-more-badass darker uniforms who do actually observe real infantry tactics and perform the scout work. Only War also mentions that each Infantry Squad receives a Leman Russ tank for support. Not a Command Squad. An Infantry Squad. That might be a line of men firing at you, but that line has a dozen or so tanks right behind it, firing all of their guns. Has you play as an armored regiment and be tank crew, not the infantrymen of an infantry regiment, which do not get tanks. Its expansion, Hammer of the Emperor allows for mixed regiments. Besides, fluff and game-play do not always agree with one another.

However, one must note that the fact that they're never taking cover means that they're not spending any time not aiming or not firing, meaning that relative to other armies, they could keep you pinned a whole lot more easily. So while they might die off really quickly, they'll do a hell of a lot before they drop.