Orel Amphibious Corps

The Orel Amphibious Corps are a type of specialist forces within the Imperial Army, originating from the oceanic Haven World of Orel, in the Corusco Cluster. As their name implies, they are trained for operations underwater and in amphibious assault, though the three-dimensional awareness their training requires also makes them capable in Zero-G environments. Though amphibious assaults are rare in the Imperium due to the preference for air power, the specialization maintains a niche use on worlds heavily dominated by water, or ones with heavy anti-air defenses

## History

Due to the unusual nature of Orel as an ocean world, most conventional modes of warfare are completely unusable. There is no soil to dig trenches in, no terrain to take advantage of, and no high ground to try to hold. There is only water and man-made superstructures. When it was originally colonized, Orel was a luxurious resort world whose entire economy was geared on tourism. As it had little in the way of strategic importance, matters of defense were a very low priority, and only some defense forces were kept to ward off the occasional pirate or xeno raid. This changed with the sudden coming of the Warp Storms that heralded the Age of Strife. Suddenly cut off from the rest of the galaxy, Orel's tourism-based economy crashed overnight, causing massive chaos and upheaval. The world needed to re-invent itself and to see to its own survival and industry.

The transition was not entirely bloodless, and the planet briefly descended into factionalism, split over both the limited available resources, and the minds who preached their vision as to how to weather the crisis. The warfare that spawned from this was highly atypical. It involved amphibious assaults using ships and submarines trying to capture this or that floating or underwater city, but due to the lack of solid ground, the potential destruction of one of the planet's then wholly irreplaceable living spaces was too much to accept. As a result, infantry invasion to take over major marine cities with minimal structural damage quickly became the norm, even though the planet had access to much more devastating weaponry, such as bluewater warships with firepower rivaling Titans. From this need to capture marine cities with infantry as intact as possible, the various predecessors to the modern Orel Amphibious Corps were born.

Before long, the attention of the people of Orel turned outwards after their re-unification, in order to protect themselves against the various raids of xenos and invaders. The lack of anything even resembling a traditional landing zone to ferry troops made attacking Orel at all a daunting process, as any real assault would have to be started by securing one of the marine cities, which involved an orbital assault under significant air and orbital defense fire. This did not always deter maddened Xenos however, nor would it deter the Imperium itself when it would come to subjugate the Cluster, and although they mostly served as security forces during peace time, with their main threat being marine predators, they remained fairly experienced in their preferred mode of warfare.

After Orel was folded back into the Imperium by force, the OAC in their current form were created, as the Imperium understood the value of such specialist troops, even if air assaults were generally more common and convenient on most worlds. Very few worlds could provide the sort of expertise that Orel could, and it would prove useful in scores of niches or unorthodox situations from the days of the Compliance to the 41st millennium. Even on worlds that did not have sprawling oceans, the OAC's ability to completely evade detection - as well as disengage from an overwhelming pursuer - by moving through rivers and lakes made them an extremely useful assets, enabling Imperial commanders to engage in unorthodox warfare that most foes were not ready for.

## Doctrine

The Orel Amphibious Corps are a formation capable of fighting both underwater and on solid ground with no change in equipment. As such, they make great use of stealth and surprise in their operations. They are a fairly aggressive and fairly mobile formation, preferring to strike hard and fast at short range and to keep moving to avoid counter-attacks rather than stand and fight to hold ground. Much like airborne drop troopers, the typical OAC squad cannot carry heavy weapons, which puts them at a disadvantage in a head on confrontation with a standard ground formation that does possess such weapons. That is part of why they prefer to avoid such head-on confrontations, relying on outflanking, rapid surprise assaults, and strike-and-fade tactics.

Because of this preference for stealth and their unusual travel routes, small squads of the OAC attached to typical Imperial regiments on any world but an arid desert world can be used for reconnaissance, traveling underwater along the waterways and rivers until they reach the heart of an enemy camp, at which point they can engage in simple observation or even sabotage. Larger groups following the same tactic can easily storm enemy rear positions that did not expect to see combat, destroy their supplies, vehicles or artillery with demolition charges, then swim their way back upstream. Thanks to the solid insulation of OAC Diver Armor, they can even enact this sort of tactics on frozen worlds or on temperate worlds under winter or arctic conditions, where they simply travel below the ice, then cut off an egress point through it with las-cutters mounted on underwater weapon platforms once they reach their destination.

The depth and pressure that individual Diver Armor can withstand is enormous, equivalent to that of military submarines of Terra's early days and allowing OAC infantry forces without accompanying submarines to travel at depths where they are effectively invisible even to active sonar. This is still however but a shallow kiddie pool compared to the crushing depths of Orel's deepest abyssal trenches, which can reach hundreds of kilometers deep. To reach depths below 500 meters, the OAC makes use of its wide arsenal of combat submarines, some of which are pure transports used for delivering breaching parties to seafloor bases, but others carry considerable amounts of cruise or ballistic missiles, which can support landing forces from far away and destroy heavy fortifications just ahead of the infantry's assault. Most of these submarines - those still on Orel at least - are fitted with gravitic shielding, as even mankind's spectacular advances in material sciences cannot hope to withstand alone the crushing weight of 10'000 atmospheres.

The OAC also makes use in limited numbers of a more advanced type of diving suits that is far more expensive than typical Diver Armor, and more akin to power armor. These suits which vaguely resemble a more shark-like version of Terminator armor and is mounted with several tiny pump-jet maneuvering nozzles can withstand the crush depth of Old Terra's deepest former oceans at 1'000 atmospheres and can be made even more resilient by mounting miniaturized versions of the aforementioned gravitic shielding, but such suits are exceedingly rare. They are sometimes used as shock troops in assaults that are deemed too difficult to even attempt otherwise, but they have very poor mobility on the surface.

## Wargear

* **Mk.VI Diver Armor** - Orel Dive Armor was designed primarily to resist harsh underwater conditions, and as such despite being fairly bulky and more expensive than Guard flak armor, it provides no additional protection compared to standard flak armor. It is built out of sturdy weaves of cabron fibers, elastomer and thermoplas, which give it its tough but somewhat flexible construction and its resistance to shrapnel and low-power impacts. The suit is also reinforced by compressible fluid bladders and an insulating aerogel layer. Standard Diver Armor is capable of withstanding a pressure of up to 50 atmospheres, or 700psi. It is also fitted with a helmet with integrated micro-bead, auspex unit and light projector, as well as a self-contained breathing apparatus using the same kind of oxygen recycling equipment as power armor for long underwater autonomy.
* '**Aquamarine' Pattern Mk.III Lascarbine** - Creating a weapon that can function as well in and out of water has always been a harrowing task because it combines two environments that obey to entirely different conditions and dynamics. Through no small amount of perseverance however, the Aquamarine pattern was created. Due to the effect of fluid dynamics on bullets, a Las weapon was deemed to be the best base to work with, but water dispersion still considerably affected the theoretical maximum range of any underwater laser. In order to minimize energy loss over a distance, the Aquamarine was designed to function with an extremely short wavelength and a focusing lens. It is distinctive by its bright blue beam and the hissing sound it produces, as well as the fact that it was also designed to take advantage of water-cooling whenever submerged to be able to attain higher energy levels than on the surface. Outside of the water, it functions as any other standard lasgun would. Submerged, its range is halved, but its penetrative power is greatly increased. The Aquamarine is also fitted with an under-barrel launcher for Pressure Bombs
* **6x Charge Packs** - Each Munitorum standard power pack is good for 50 shots in regular conditions, but the Aquamarine pattern takes up slightly more power underwater, only being able to fire 30 shots before needing to be reloaded. As such, an extra two charge packs were needed to get close to the standard 200 shots of the average guardsman.
* **3x Pressure Bombs** - Roughly half-way between a tiny depth charge and a missile, Pressure Bombs are heavy high-explosive charges with a very small pump-jet nozzle that allows it to move forward underwater where attempting to simply throw the grenade would be totally ineffective. On the surface, it can be used as a high-power frag grenade to take out infantry, though its range is somewhat reduced due to its relatively heavy weight. Underwater, the overpressure wave they create is greatly amplified, giving them even more considerable power.
* **Mono-Trident** - It is not uncommon for guardsmen to have an utility knife that doubles as a bayonet to mount on their lasgun. The OAC troopers are no exception, but with the small detail that the bayonet atop their lasguns is, in fact, a trident blade. This is partially due to the fact that thrusting weapons are considerably more effective than slashing ones underwater.

## Notable Orel Amphibious Corps Units

* **22nd OAC Fulcrum** - The 22nd was originally one of the several units assigned to the defense of the abyssal megacity of Fodray during the Imperial subjugation of the Corusco Cluster. It is the only one that survived the battle without being reduced to a combat-ineffective shadow of its former self and was able to wound enough Astartes of the IInd Legion to earn their respect, and subsequently, a place alongside them in the greater Compliance. It is one of the few units that managed to survive the Inter-Legionary Wars up to and into modern times and is well known for its resilience
* **1st Typhoon Guards** - One of the only formations of the OAC to be entirely equipped with Abyssal Armor and 'Aquamarine' pattern assault multi-las, the 1st Typhoon Guard was raised to defend the Armory World of Typhoon, an extremely hostile ocean world that orbits not a star, but a black hole. As Typhoon was one of the most important strategic reserves in the entire Corusco Cluster during the Imperial Compliance and the subsequent Inter-Legionary Wars, no expense was spared in building it on one of the most impossible to assault worlds that could be found, and the Typhoon Guards were equipped to be able to fight in that hellishly hostile environment.