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'''Port Maw''' refers both to the [[Imperium|Imperial]] [[hive world]], its three large Naval Stations (one of which is the '''Nexus System''' - Fleet Command for [[Battlefleet Gothic]] and the [[Gothic Sector]]'s largest shipyard and repair station), and its significant support network of orbital stations and installations.{{fn|1e}} Located within what is now the [[Port Maw Subsector]], it is currently the sector capital of the [[Gothic Sector]] of [[Segmentum Obscurus]].{{Fn|2}} During the [[Great Crusade]] and [[Horus Heresy]], it served as a major naval installation for what was then the the [[Coronid Deeps]].{{Fn|3b}}

An artificial planetoid^{[[Port Maw (planet)#Conflicting Sources{{Fn|[See Conflicting Sources]]]}sources}}, Port Maw distantly orbits around a larger and (at least during the [[Great Crusade]]) more habitable planet called '''[[Æstellica]].'''{{Fn|3a}}

*{{Main|Coronid Deeps}}

An artificial planetoid, port maw was discovered by the '''[[60th Expeditionary Fleet''' ]] in a region of space then known as the [[Coronid Deeps]]. Observing the 500 kilometer kilometre wide aperture in the planets planet's surface, giving it the appearance of a vast fanged mouth, the members of the fleet would give it its eponymous name: '''Port Maw.'''{{CME}}

In 001.[[M31]], in the final years of the [[Great Crusade]], an [[Imperialis Armada]] facility would begin construction at the direct behest of the [[Officio Astra]], as part of a strategic plan to consolidate fleet assets and operational structures in the region following the triumph of the [[Ullanor Crusade]] and the appointment of [[Horus Lupercal]] as [[Warmaster]]. It was intended for Port Maw to become one of the most powerful naval facilities in the entire northern Imperium. The hollow artificial planetoid offered unparalleled defense defence against assault to developments and facilities inside its core, while construction began on vast trans-orbital dockayrdsdockyards, battlestations and provender belts in the surrounding star system.{{Fn|3a}}

Port Maw's fleet anchorage would be one of a handful of massive fleet bases situated on the borders of the Imperium. Though still dwarfed by [[Battlefleet Solar]], they were built by an Imperium that had largely conquered the galaxy, rather than one which set out to conquer it. At least one of these was built in each [[Segmentum|Segmentum Majoris]] Majoris, with more planned, to hold and defend a galaxy so hard fought over. As such, they functioned as ports of supply and muster, command-and-control, and as home bases for a permanent armada of warships with their own armies of [[Imperial Army|Auxilia]] troops. They would serve as a source of deep range patrols and rapid-reaction forces to respond to sudden threats such as civil-disturbances, rebellion, or attacks from within or without the Imperium's new borders.{{CME}}

The Port Maw armada outnumbered and likely out-gunned any single [[Expeditionary fleet Fleet]] of the Great Crusade, at least on paper. Made up of several hundred first and second rate ships of the line, various [[cruiser]]s and assault vessels intended to dominate 'small wars' and conduct long patrols, as well as [[frigate]]s and [[destroyer]]s meant for escort duty, destroy marauders, and hunt those who would disturb the Emperor's Peace. Such fleets possessed fewer large capital class ships than the conquest forces of the Great Crusade, but those they did possess were often powerful examples of the type, such as ''[[Goliath Class Battleship|Goliath-]] '' and [[Legatus Class Battleship|''Legatus''-class]] [[battleship]]s - strong support-intensive designs that had been replaced in frontline service by [[Gloriana]] and [[Victory Class Battleship| Victory]] patterns.{{CME}}

Unlike the fleets of the [[Legiones Astartes]], [[Explorator Fleet]]s, and [[Rogue Trader]]s, these fleets were defensive in nature, able to be piecemealed into smaller commands as needed and were manned by [[Solar Auxilia]] almost exclusively, without any transhuman (i.e. [[Astartes]]) components, and outside the typical command structure of the great crusade. Their [[Imperial_Navy_Hierarchy#Admiralty_Ranks| Grand AdmiralAdmirals]]s and [[Lord_GeneralLord General| Lord MarshallMarshalls]]s operated under orders directly from the [[Council of Terra]], and were equal or greater in authority to the [[Lord Commander (Legiones Astartes)| Lord CommanderCommanders]]s of individual planets their ships protected. Of course, in practice, it was a foolish Grand Admiral that did not defer to a [[Primarch]] or an emissary of the Terran Court or [[Mars]], but this represented a growing distance between the nascent Imperium's forces of conquest and those of defensedefence. As such, the Traitors influence on these forces in the opening of the Horus Heresy were lessened. This would be demonstrated during the [[Horus Heresy]] where those traitor elements of Port Maw's Warfleet that turned were conducted by a minority mutiny or by cadre's of traitor officers, rather than wholesale forces swearing to the Warmaster.{{Fn|3e}}

*{{Main|Manachean War}}

===Miniatures===