Overview of the Warhammer 40,000 universe
The Gaunt's Ghosts novels are set in the long-established Warhammer 40,000 universe, although they require no foreknowledge of the rest of the setting. Developed by a team at Games Workshop led by Rick Priestly, the Warhammer 40,000 tabletop wargame was launched in 1987 as a SF companion to the older Warhammer Fantasy Battle game. WH40K (as it is popularly known) was a major success, spawning a number of spin-off boardgames (the best-known of which are Space Crusade and Space Hulk) and a glut of computer game adaptations, the most popular of which is the Dawn of War real-time strategy game series from Relic and THQ. It also spawned a line of original fiction, initially edited by hard SF author Stephen Baxter and featuring work by 'proper' SF author Ian Watson, whilst noted SF critic David Langford worked on the related White Dwarf magazine for a time. The setting was heavily inspired by Frank Herbert's Dune universe and Robert Heinlein's Starship Troopers, with additional influences from the works of Michael Moorcock (the order/chaos conflict) and films such as Aliens (even if the Space Marines of WH40K are nothing like the marines of the Cameron movie), but is most notable for its almost nihilistic tone.
The WH40K setting is the Milky Way Galaxy, almost 39,000 years into the future (the 'current' year in the setting is AD 40,999). Humanity has expanded into space and colonised millions of planets across the Galaxy by travelling through the extradimensional Warp. At one time humanity achieved a state of monumental technological achievement, existing alongside powerful robots and AI (for undisclosed reasons AI was later outlawed and robots - 'iron men' - held to be anathema, possibly for religious reasons). Unfortunately, a sudden rise in Warp Storms saw many worlds, including Terra (Earth) cut off from the rest of the colonies. Many worlds, dependent on trade for food and supplies, starved to death. Others fell into anarchy and civil war. The Warp Storms were the result of the activities of a hubristic alien race known as the Eldar (space elves) who had become corrupted by the dark, extradimensional beings living within the Warp (known as the Chaos Gods). The Eldar all but destroyed themselves in a titanic eruption of Chaos, allowing the birth of a new Chaos God and tearing open a hole in the fabric of reality known as the Eye of Terror and allowing the forces of Chaos easier access to our universe. On the plus side (not much consolation to the trillions of humans and Eldar who had died during the preceding centuries of anarchy), the Warp Storms did now abate.
The end of the Warp Storms allowed the human worlds (now much depleted) to reestablish contact with one another, but their weakened state made them easy prey for raids, invasions and attacks by other alien races, such as the Orks. On Terra, a local warlord had risen to take control of the entire planet, followed by the rest of the Solar system. Proclaimed the Emperor of Mankind, he launched a Great Crusade to reunite humanity under one flag. Over the course of two centuries the Emperor led this task, aided by the genetically-engineered, towering super-humans known as the Adeptus Astartes, the Space Marines, whose twenty legions exterminated almost all resistance to the Emperor's will. At the moment of triumph, however, just as it appeared that the new Imperium of Mankind would regain the glories of earlier epochs, the Emperor's most valued servant fell to the forces of Chaos. Horus, the Primarch of the Luna Wolves legion, was corrupted and led almost half of the Marine legions in rebellion against the Emperor in a lengthy civil war known as the Horus Heresy.
Horus and the Emperor confront one another at the end of the Heresy. They sat down and over a cup of tea sorted the whole thing out peacefully.
At the end of the Heresy, Horus's forces launched a full-scale assault on Terra itself, but were defeated. The Emperor and Horus faced one another in combat and the Emperor prevailed, but only at the cost of many terrible wounds. To save his life, his servants installed him in a life-support machine to which he is now permanently bonded and cannot leave, and is now part of the Golden Throne itself. The Emperor, now often called the God-Emperor of Mankind, has spent ten millennia within the Golden Throne, his immense psychic powers being used to help protect the Imperium from the depredations of Chaos and maintain psychic beacons making travel through the Warp safer.
These events took place approximately ten thousand years before the 'present' of the WH40K setting. The Traitor Legions, also called the Chaos Space Marines, withdrew to the Eye of Terror and the surrounding regions, occasionally launching devastating counter-attacks against the Imperium. The Imperium developed a number of institutions (most notably the Inquisition and its own psykers) to guard against the corruptions of Chaos and prevent a repeat of the Heresy, as well as raising new Space Marine chapters and employing tens of billions of 'normal' humans in a military force known as the Imperial Guard. Unfortunately, the Imperium's desire to utterly annihilate the forces of Chaos was thwarted by a near-continuous series of wars with various alien races (including the Orks, the arrogant Eldar, the disturbing Necrons, the rapacious Tyranid swarms and the technologically-advanced Tau) and the sheer complexities of running and defending a empire consisting of millions of worlds and quadrillions of inhabitants.
Warhammer 40,000 is notable for its extreme bleakness and sense of inevitable doom, characterised by fans as being 'grimdark'. There are no real 'good guys', with all of the races (aside from the Tau, who like other races as long as they do what they are told) noted as being extremely xenophobic and living in a state of near-permanent warfare. Humanity is enthralled by a theocracy which commands insurmountable resources, with little chance of overthrowing the God-Emperor. Indeed, despite the appalling conditions much of humanity lives under in the 41st Millennium, the Imperium is nevertheless presented as being the best of several bad choices. Also, whilst conditions are pretty bad on the industrial hive worlds (where billions toil in city-sized factories to build weapons and vehicles for the Imperium's military), there are agrarian worlds where a slower, more peaceful form of life can be found (such as on Tanith). It's a dark universe where chaos and bloodshed are rife, and people survive the best they can.
The Sabbat Worlds Crusade
In the 35th Millennium the forces of Chaos threatened a cluster of 100 inhabited worlds near the outskirts of Imperial space. A simple shepherd's daughter, Sabbat of Hagia, elected to join the fight against the forces of Chaos after experiencing a holy vision of the Emperor. Sabbat's vision and tactical abilities saw her rise to lead a huge offensive against the Chaos forces which eventually succeeded in driving them from the sector. Sabbat was killed in an epic battle on Harkalon at the end of the war, was beatified and the entire star cluster was named in her honour when it was integrated into the Imperium as a secure territory. Sabbat was held in particularly high honour by the White Scars Space Marine chapter, who gave her the unprecedented honour of forging a suit of Astartes power armour for her (almost unheard of for normal humans, let alone women, since the Astartes are all male).
Three thousand years later, the forces of Chaos began to infiltrate the Sabbat Worlds cluster to weaken it from within. A series of wars, civil wars and various conflicts began which the Imperium managed to restrain, but never entirely eliminate. By 740.M41 (the 740th year of the 41st Millennium, or 40,740 AD by the old Terran calendar) many of the Sabbat Worlds had been overrun by Chaos insurgents, bolstered by enemy forces arriving from outside the sector, and the Imperium of Mankind officially abandoned the cluster, withdrawing to more heavily-defended systems. The forces of Chaos had appeared to have triumphed.
Of course, the abandonment of over a hundred imperial worlds and trillions of imperial citizens to the Ruinous Powers could not be countenanced. An influential imperial general, Warmaster Slaydo, heavily campaigned for a military effort to be made to retake the sector in the name of Saint Sabbat and the God-Emperor. The High Lords of Terra, speaking for the Emperor, agreed that Chaos could not be allowed to take root in these worlds and authorised a massive counter-offensive known as the Sabbat Worlds Crusade, one of the largest military operations since the Horus Heresy.
Warmaster Slaydo assembled a force of approximately one billion Imperial Guard, consisting of around four hundred thousand regiments (of which the Tanith First and Only, Gaunt's Ghosts, is precisely one). Slaydo also received assistance from six Adeptus Astartes Chapters, including the White Scars, and a number of Imperial Titans (gargantuan Imperial war machines capable of levelling entire cities). In support was a significant detachment of the Imperial Navy, consisting of (at the very least) thousands of capital ships and millions of transports. Slaydo launched the Crusade on the 266th day of 755.M41 with a massive assault against outlying worlds in the cluster. The initial shock of the attack won the Crusade several worlds very quickly, but the forces of Chaos mounted a significant counter-offensive, reducing the Crusade to a hard grind over the next decade. Frustrated with the slower-than-anticipated progress, Slaydo sought to regain the initiative with a surprise attack on Balhaut, the sector headquarters for the Chaos Archon overseeing the war, Nadzybar. The attack was successful, with Balhaut falling in several weeks of exceptionally heavy fighting. Nadzybar was killed, but so was Slaydo. On his deathbed, he appointed a junior but extremely promising general, Macaroth, to take his place.
Enter the Ghosts
Following the devastating assault on Balhaut, there was an urgent need for reinforcements. The agricultural world of Tanith, located close to the Sabbat Worlds, was ordered to raise three regiments for the Imperial Guard, and Colonel-Commissar Ibram Gaunt, who had distinguished himself on Balhaut, was dispatched to take command of them. Unfortunately, a small Chaos fleet escaping from the Balhaut system, burning everything in its path, attacked Tanith shortly after the Tanith 1st had begun embarking on its transports. Gaunt, realising the hopelessness of the tactical position, ordered the Tanith 1st to abandon the planet and flee, only hours ahead of the total destruction of the planet. The officers and soldiers of the 1st were divided by this move, some agreeing it to be tactically sound (whilst regretting they could not stand and protect their homeworld, even unto death) whilst others believed it to be cowardly and dishonourable. These latter troops took some considerable time to forgive Gaunt and fully accept his authority.
The Tanith 1st, now dubbed the Tanith First and Only, for there would never be another regiment raised from that world, was nicknamed the Ghosts, for being the last survivors of a dead world and people, and also for their elite camouflage abilities and camo-cloaks that rendered them almost invisible in the right lighting conditions. Over the course of the Crusade they would achieve many significant and impressive military victories. However, whilst the Tanith 1st's achievements are notable, they are not presented as being central to the Crusade, with the Ghosts often achieving victories on the flanks or sidelines whilst the central, major thrusts of the war take place elsewhere. Their defence of the Saint on Herodor in Sabbat Martyr is arguably their most notable victory (in tactical terms) to date, although their tenacious defence of Vervunhive in Necropolis is probably their largest single military achievement.
There are currently twelve Gaunt's Ghosts novels in print, along with several spin-offs. A thirteenth book is due next year. For ease of collection, the first eleven books have been collected in three omnibus volumes, corresponding to the story arcs the series is divided into. The twelfth through fifteenth volumes will form a fourth omnibus and arc, and it is unknown if the series will continue beyond that point. I would hope not, however, as fifteen books is enough for any series, and beyond that Abnett could risk turning into Bernard Cornwell, churning out Sharpe books for the money despite increasingly ludicrous scenarios (so Sharpe was at Waterloo and Trafalgar? Really?).
Omnibus I: The Founding
1. First and Only
Omnibus II: The Saint
4. Honour Guard
5. The Guns of Tanith
6. Straight Silver
7. Sabbat Martyr
Omnibus III: The Lost
8. Traitor General
9. His Last Command
10. The Armour of Contempt
11. Only in Death
Omnibus IV: The Victory
12. Blood Pact
13. Salvation Reach (forthcoming)