Imperial Navy

In the fictional universe of Warhammer 40,000, the Imperial Navy is one of the armed forces of the Imperium of Man.

While the Imperial Guard is responsible for the Imperium's ground forces, the Imperial Navy is responsible for the fleets of starships that maintain order between the stars and planets in the Imperium, as well as engaging threats both inside and outside the Imperium's borders.

The Birth of the Imperial Navy
During the Great Crusade, both the Guard and Navy were originally a single organisation; the Imperial Army. Each formation of the Imperial Army was assigned a cruiser-size vessel to act as a transport and mobile base, which was usually accompanied by several escorts. Commanding Officers held command over both their regiment and the starships assigned to them.

The events of the Horus Heresy caused a rethink of military organisation that, among many things, split the Army into the Guard and the Navy, so that no one commander could control both an army and the means to transport that army across space. This makes rebellions easier to contain.

Ships of the Imperial Navy
Fleets of the Imperial Navy are made up of multiple vessels that can be divided into three broad categories; battleships and grand cruisers, cruisers, and escorts. The actual size of starships in the Warhammer 40,000 universe is debated, although it is generally accepted that cruiser-size starships are between 3 and 6 kilometres in length.

Battleships are huge ships, with enormous amounts of weapons and shields, and are usually the command position for the Admiral of the Fleet. Although very powerful, battleships are slow to manoeuvre. Battlefleet Gothic employes two classes; the Emperor (which could carry a sizable amount of attack craft next to its normal weaponry) and the Retribution (which was noted for its powerful broadside firepower and its large amount of torpedo tubes). Battleships of Battlefleet Armageddon are based on the older Apocalypse and Oberon classes.

Grand Cruisers are smaller than battleships, yet larger than cruisers. These vessels are usually much older in design and do not incorporate many of the features that are typical in current Imperial Navy vessels, like the armoured prow, and are not quite compatible with current navy tactical doctrine. As such, many are retired from active duty, but are still used by reserve fleets. The Avenger, with its powerful broadside firepower, is one such example.

Cruisers make up the majority of a fleet. Though not as powerful as a battleship, cruisers are much faster and can still deliver a deadly blow. There are multiple classes of cruiser; most based on the same general hull design but incorporating different combinations of broadside batteries, lance turrets and starfighter hangars. Examples include the all-round Lunar-class, the Gothic with its powerful lances and the Dictator starfighter and attack craft carrier.

Note there are also classes of battlecruisers. Although based on a hull-design that is similar to the regular cruisers, these ships are generally more heavily armed. A notable example is the Mars-class battlecruiser, with its fighter bays, broadside batteries, lance turrets and immense Nova cannon.

A subset of the cruiser category contains the light cruisers. These ships fall in size between cruisers and escorts, mixing the firepower and durability of the former with the speed and manoeuvrability of the latter. The Dauntless is a very common light cruiser class in the Imperial Navy. Self-sufficient, fast and has enough firepower to be a threat to both escorts and capital ships.

Escort ships are the smallest type of ship in the Imperial Navy fleets. They are usually organised in squadrons of 3 to 5, though larger squadrons are not uncommon. The main task of the escort ships is to draw fire away from the capital ships so that they can get into position quicker and safer. Most escort classes specialise in a certain role, such as the Cobra-class torpedo boats or the Firestorm with its armour-piercing lances.

Imperial Fleets
The Imperium is divided into five 'Segmenta'; Solar, Obscuras, Pacificus, Tempestus and Ultima. Every ship of the Imperial Navy is assigned to one of these Segmentum, and falls under the command of the respective Lord High Admiral.

In turn, each Segmentum is divided into 'sectors', regions of space that are generally cube-shaped and contain 8 million cubic light years of space. These sectors contain multiple sub-sectors, collections of star systems no more than twenty light years in radius. The ships of each Segmentum are divided amongst the sectors. These Battlefleets are assigned the task of safeguarding the sector they are assigned to, each Battlefleet is generally named after the sector it is assigned to (Battlefleet Gothic is located in the Gothic sector, Battlefleet Cadia is located in the Cadian sector, etc).

Each Battlefleet is assigned a number of cruisers and battleships, usually between fifty and seventy-five vessels. The Battlefleets are also assigned multiple squadrons of escort starships, and is also in command of a large number of transports, messenger craft, orbital defences, space platforms and system patrol vessels. The ships of a Battlefleet must constantly patrol their sector and fulfil a variety of roles; protect merchant shipping from pirates, transport Imperial Guard regiments to warzones, escort Adeptus Mechanicus Explorator fleets and provide orbital support for invading or defending armies.

Because of the vast space that requires policing, the Battlefleet is normally split into detachments consisting of one or two cruisers, accompanied by a squadron of escorts. If a particular situation is more than a detachment can handle, additional detachments are called in to reinforce.

On occasion, a Battlefleet can be formed to operate in a smaller area. Battlefleet Armageddon is assigned solely to the Armageddon sub-sector, and, prior to the Third War for Armageddon, was made up of four battleships, twenty-seven cruisers and thirty six squadrons of escorts. Battlefleet Solar is assigned specifically to the Sol System, and is primarily charged with defending the two holy worlds of Terra and Mars.

Fighter Squadrons
Many Imperial Navy capital starships are capable of carrying starfighter squadrons. These are used in a variety of roles, from small fighters providing defence against torpedo attacks, to heavy bombers packing anti-ship ordnance.

The Fury Interceptor is the most common starfighter used by the Imperial Navy for space combat. The Fury is significantly larger then most atmospheric fighters, and carries a pilot, navigator and gunner. On occasion, an Astropath psyker will also be aboard, to provide greater communications capability. They are equipped with multiple forward-firing banks of lascannons and anti-starfighter missiles.

Starhawk bombers are larger, slower craft, designed to carry a heavy payload of plasma bombs and armour piercing missiles, for use against enemy capital ships. Starhawks are also equipped with short-range defence weapons, used to fend off enemy starfighter squadrons. On rare occasion, Starhawks can be modified to carry and launch a very small number of anti-starship torpedoes.

Atmospheric Fighters
As part of the post-Heresy reorganisation, all aviation capability was assigned to the Imperial Navy. No Imperial Guard regiment (with the possible exception of the Phantine Air Corps) has access to atmospheric fightercraft, and the assistance of the Imperial Navy is required when air support is needed for a campaign.

For atmospheric fighter combat, the two workhorses of the Imperial Navy are the Lightning strike fighters and the Thunderbolt heavy fighters. The Lightning is the faster of the two, but cannot carry as many weapons as the Thunderbolt, and are considerably lighter armoured. Lightnings are often used as reconnaissance aircraft and interceptors, while Thunderbolts are mainly assigned to an air superiority role.

Marauder bombers are huge aircraft, capable of carrying two thousand kilograms of ordnance. Each Marauder possesses a massive bomb bay, along with many autocannons and heavy bolters, the latter two used to protect itself from enemy air support.

For close support, the Imperial Navy has access to Valkyrie transports, and the Vulture gunship. These aircraft are not true flight craft, instead using vectored thrust to travel quickly at low altitudes.

Offensive Weaponry
Weapons Batteries usually are the primary armament for most warships. Since each battery consist of numerous ranks of individual weapons, whole sections of the ships' hull can be covered by gun ports, launcher systems, turrets and weapon housings. The weapons employed vary immensely: plasma projectors, close-range missile launchers, laser cannons, rail guns, fusion beamers and graviton pulsars have been found on Imperial ships. These batteries fire in co-ordinated salvoes, to increase the chances to hit and amount of damage done to a target.

Lances are energy weapons of extreme power. Usually mounted in large and heavily armoured turrets, lances use triple or even quad energy projectors to focus its energy into a concentrated beam, capable of burning through even the most armoured hull and cutting smaller vessels in half.

Torpedoes are long range missiles carried by many Imperial Navy vessels. Over sixty meters long, these weapons are powered by a plasma reactor which also doubles as its warhead. Once launched, the plasma drive propels the torpedo towards its target, whilst starting an energy build-up that will detonate the projectile once it reaches its target. Most torpedoes only have limited detection capabilities and will not track and engage its target unless its passes within a few thousand kilometres of the target vessel. Contrary to weapons batteries and lances, torpedoes cannot be deflected by a ship's shields.

Nova Cannons are huge weapons. Normally mounted in the prow of the ship so that the ship's engines can compensate for the recoil, these guns use gravimetric impellers to propel a projectile close to the speed of light. After reaching a preset distance, the projectile implodes with a force potent enough to cripple most vessels and/or damage several at once.

Defensive systems
Every Navy vessel is covered with defensive turrets designed specifically to destroy incoming bombers and torpedoes.

Shields are protective energy barriers that allow ships to survive the hostile environment that is space. Shields form an invisible band of energy around the vessel, a variable layer of force that can absorb radiation, interstellar dust, particle showers and weapons hits. Shields have a maximum tolerance and can be overloaded by sustained fire, forcing the generators to shut down to vent off excess energy.

Every spacefaring vessel is equipped with a certain amount of armour, capable of deflecting impacts on the ships' hull. Typical for the Imperial Navy however, is the armoured prow that is capable of defecting all but the most powerful of frontal hits.

Propulsion systems
Every Imperial ship is equipped with a plasma drive for normal propulsion through the depths of space. Running up to a third of the ship's length, the aft section is a mass of drive tubes, engine compartments and plasma reactors.

Most Navy ships employ warp drives to breach the barrier that separates realspace from the Immaterium and allow for interstellar travel. Implosion of these drives can lead to the creation of a warp rift.