Vigo sector is a large Imperial sector in Segmentum Tempestus, not very far from the edge of the Imperium, almost surrounded by wilderness space.
During the war against Hive Fleet Leviathan, Vigo sector was cut off from reinforcements by order of the Munitorum to allow these forces to be used against the Tyranids; the timing was inopportune, as shortly after that, the sector was invaded by the forces of Chaos, and several Ork Waaaghs.
Karlees Navarre, a skilled but unpopular and semi-heretical officer, bribed and blackmailed his way to be appointed commander of all Imperial forces in Vigo; he rallied the remaining Imperial forces, and in a few years, liberated all of Vigo sector.
Vigo Sector extends like an isthmus into Wild Space, surrounded on almost every side by Xeno empires such as the Ork Samarkh Worlds.
Vigo Sector is nearly twice as large as a 'normal' sector, and includes the worlds of many other sectors have either fallen or been abandoned over the past millenia.
It comprises 9 subsectors:
Yggdrasil; a large, heavily-populated subsector, closest to Imperial space, and so the least hard hit by the wars.
Quirkitai; includes the sector capital, Kommanche;
Rochese; a cul-de-sac of a subsector, includes mostly Agri- and Fudal worlds; includes Tomnason, the current monastery-world of the Black Hornets Astartes Chapter.
Dorsai; A heavily-industrialized subsector, including many Hive worlds; hard-hit by the Ork Waaaghs of Azhrag the Slaughterer.
Tal; A subsector of generally very pious worlds, a small Order of Battle Sisters; the Order of the Crimson Sash, has been banished from Terra and come here on a penitent crusade.
Skarlett; all that remains of Menchek sector; a densely-populated subsector, filled with the descendants of refugees.
Malakai; Another densely-populated subsector; it used to be part of Uthor sector.
Polak 'sector'; a small subsector, the remaining worlds of Polak sector, absorbed into Vigo after Polak sector was abandoned; due to a clerical error, it is still often referred to as Polak sector in Adminitratum files.
Dubrovik; a small subsector; used to be part of Uthor sector.
In the galactic east side of the sector lies the 'Devil's eye' a large Warp Rift that spews forth Warp energy, ancient ships, and Chaos raiders; in 997.M41, an uninhabited Craftworld, later named Marathag fell out of the Warp there.
To the Galactic North lies the Samarkh Worlds; once a bustling Imperial sector, it is now an Ork empire, from which many Waaaghs! have descended on Vigo.
Vigo is a crowded, poor sector, rife with mutation, heresy, and corruption.
But it wasn't always that way: in past ages, this was a much larger area of Imperial spaces, including many other sectors surrounding Vigo. But over the past Millenia, every other sector has either fallen to corruption, Xeno invasions, or simply been abandoned when Imperial forces could no longer defend them; their remaining worlds were absorbed into Vigo, billions of refugees stretching the sector's resources to the limit.
The Devil's Eye, a great warp rift in the midst of Vigo, has been a constant source of trouble, spewing forth Warp energy, causing mutation, and bringing constant Chaos raiders, testing the endurance of the sector's defenders.
Finally, in 4561996.M41, Toran the Murderer, a Chaos warlord gathered an enormous fleet and invaded Vigo; though his initial invasion was turned back by Lord-Admiral Ulrik at great cost, an Ork Waaagh! weakened the sector further, and Toran invaded again.
Lord-Admiral Ulrik, and the majority of the Sector fleet, sacrificed themselves defending Quirkitai, buying time to evacuate many of the worlds to Yggdrasil and Rochese sectors.
It was shortly after that, that the Departmento Munitorum(perhaps ignorant of the scale of the defeat) ordered that all reinforcements to Vigo sector be cut off, as the oncoming Tyranid Hive Fleet Leviathan was deemed a a far greater threat.
A highly skilled, but unliked and semi-heretical Imperial officer, Karlees Navarre obtained the command of all Imperial forces in Vigo sector with the dual rank of Lord-General, and Fleet-Admiral(technically illegal, as the two services are supposed to remain entirely separate).
Rallying the remaining Imperial forces, he raised an enormous army; including an Astartes Chapter, the Black Hornets, and an order of Battle Sisters, the Order of the Crimson Sash, but also including millions of mutants, Abhumans, and seconded PDF.
The fleet was hard struck, but Navarre had his commanders capture a a number of enemy ships, and added armed merchantmen and Eldar mercenaries, including Ariel Ysggad to the fleet.
Organizing the force into three 'columns' each including elite troops; one, the Astartes of the Black Hornets, the second the Battle Sister of the Order of the Crimson Sash, and the third, the elite Iron Brigade, Navarre launched a massive offensive, quickly recaptured most of Quirkitai sector, including the sector capital, Kommanche. He then sent escort vessels haring into Toran the Murderer's territory, challenging the Chaos warlord to come and take it back.
Gathering a huge armada, Toran attacked Kommanche, sure of victory against the Imperium's cobbled-together fleet.
In what was possibly the most one-sided victory in the history of the Imperial Navy, Navarre lured Toran's fleet into concealed minefields, then attacked with massed waves of attack craft and torpedoes; despite being outnumbered nearly 2-1, the Imperial fleet destroyed and captured almost every ship in Toran's fleet, for the loss of a single Cobra Destroyer(which was easily salvaged, and most of the crew rescued).
Adding the captured ships and a number of Segmentum Tempestus reserve ships to his fleet, Navarre counterattacked into the Chaos-held systems, quickly liberating most of the Skarlett subsector; his offensive halted after the battle of Krimzon, where the Marathag Craftworld was discovered, and Navarre had to stop to deal with his Eldar allies.
After the successful handover of the Craftworld, Imperial and Eldar forces again went to the offensive, and ejected all Chaos and Ork forces from Vigo sector.
Since then, Navarre has expanded the sector's borders, recapturing worlds have lain under Xeno or traitor domination, sometimes for millenia and resettling them with the descendants of refugees from them; while the semi-heretical Navarre would normally certainly not be permitted to gain a large power base, and the defunct sectors would be revived, the normal speed at which the Administratum operates indicates that these systems will be part of Vigo sector for a long time to come.
Main article: Navarre's Reforms (Vigo Sector Imperial Forces)
Vigo sector is one of the most militarized sectors in the Imperium; every able-bodied adult is required to serve in their Planet's defense forces, and every planet is required to have a force equaling 10% of the PDF available to serve off-world in case of emergency; combined with the wide-scale use of mutants and abhumans, this means that Vigo has enormous ground forces available for whatever purpose.
The Vigo sector fleet is a ramshackle collection of converted merchantmen, Eldar allies, prizes-of-war, and regular ships produced by the Adeptus Mechanicus; composed mostly of escort ships, the few cruisers are divided between each subsector, which keeps them in reserve, while 'packs' of escort ships constantly patrol the subsectors, seeking out trouble before it grows large enough to be a threat.
Map of Vigo Sector: http://jochannon.deviantart.com/art/3D-star-map-of-Vigo-Sector-138076335