Imperial Navy (Warhammer 40,000)

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.

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, and were usually deployed with several escort starships. 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 Navy.

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, cruisers and escorts. The actual size of starships in the Warhammer 40,000 universe is debatable, 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.

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 hangers.

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

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.

Imperial Fleets
The Imperium is divided into five 'Segmentum'; 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 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 can be 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 Solar System, and is 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 equpped 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 vessels. 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-Horus 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. Lightnings are the faster of the two aircraft, but cannot carry as many weapons as the Thunderbolt, and carry considerably lighter armour. 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 flying transports, and the Vulture Gunship. These aircraft are not true flight craft, instead using vectored thrust to travel quickly at low altitudes.