A Planetary Defence Force (usually abbreviated to PDF) is a term referring to the primary military defence forces of an individual Imperial world. The PDF are under the control of the local planetary government rather than direct Imperial control; the raising, training, arming, leadership, etc., of such units is entirely in the hands of the world's Imperial Planetary Governor. According to Imperial law, all Imperial planets must maintain a standing army in order to maintain the planetary government's (and thus Imperial) control over the world against any possible invasion or insurrection. The PDF, as essentially the local military of an Imperial world, have no standardization and can take any form; some, such as the PDF of hive worlds, may be no more than legitimized gangs supported and armed by the local government to keep down the more anarchic elements. In response to any internal or external threat, it is the responsibility of the PDF to engage the enemy until Imperial reinforcements such as the Imperial Guard or Space Marines can be mustered by the nearby Sector Command. Thus, although rarely respected due to their relative lack of experience, the PDF are widely considered crucial to the Departmento Munitorum as the first line of defense for Imperial worlds against any form of invasion or rebellion. Another important part of the PDF is their role as the primary source of recruits for the Imperial Guard. Whenever required, the best soldiers in a PDF are transferred into the regiments of the Imperial Guard, receiving further training as they are shipped to their destined locations elsewhere in the galaxy. The loyalty of the PDF is not always true. Many PDF regiments will betray their planetary governor if the opportunity--and the right incentive--arises.
Suspect Loyalties
Although the PDF automatically defaults all command to any Imperial forces that arrive in the event of an emergency, there are many possible reasons the PDF or elements of it may join in rebellion against Imperial authority; Chaos or alien (particularly Genestealer) infiltration of the planet can cause divided loyalties as PDF regiments turn Traitor or are psychically enslaved by their Genestealer relatives while the sheer ambition of corrupt Planetary Governors and other organizations in control of the planet can mean the PDF under their control turns against the off-world Imperial forces. This is a cause of mistrust for PDF by the Imperium in general, and further reason for Imperial commanders to prefer to rely on non-local defenses. Imperial Inquisitors are particularly known for a lack of trust for the local PDF of a world they are investigating, and are often quick to have nearby Imperial forces available, particularly elements of the Chambers Militant of their respective Ordo, should the need arise.
Notable Planetary Defence Forces
| Regiment | Homeworld | Notable Actions |
| Agripinaa Home Guard | Agripinaa | Defence of Agripinaa during the 13th Black Crusade. |
| Armageddon Defense Force | Armageddon | Defence of Armageddon during the multiple campaigns against the Forces of Chaos (First War for Armageddon) as well as Ork forces (Second War for Armageddon and Third War for Armageddon) |
| Baran Siege Masters | Baran | Fought alongside the Raven Guard Space Marine Chapter on Baran against the remnants of the Ork WAAAGH! of Arbuttz the Incredible. Baran is a fecund world of rolling blue oceans, expansive forests, and rolling steppe land. It was originally an Eldar Exodite world, but was conquered by the Orks of WAAAGH! Arbuttz in the late 40th Millennium. By 224.M41 an Imperial Crusade passed over the world with the intention of liberating it from its Ork overlords. The first assaults quickly established the Imperial forces as masters of the steppe-lands. The Feral Ork tribes fled to the hinterlands. General von Paulus, commanding General of the Death Korps of Krieg's 127th Infantry Regiment, lacked the troops to threaten one area without exposing another, so he had a system of fortifications set up to contain the Orks instead. As the only regiment assigned to the crusade, the 127th Infantry Regiment were given the Right of Settlement of Baran. As human settlers began to arrive, these fortified positions became the basis for Imperial cities, with a curious blend of civilian structures and military fortifications. As generations passed the original conquering regiment died away and was replaced by home grown Planetary Defence Forces. Eventually, these regiments were inducted into the Imperial Guard as the Baran Siege Masters. |
| Cadian Interior Guard | Cadia | Defended their homeworld of Cadia against the encroachment of the Force of Chaos, most notably during the 13th Black Crusade. |
| Erebus Defence Legion | Erebus | |
| Kaerls | Fenris | Fought alongside their feral overlords, the Space Wolves Space Marine Chapter during the First Battle of the Fang against the Daemon Primarch Magnus the Red and his Thousand Sons Traitor Legion in the 32nd Millennium. |
| Maccabian Militia | Maccabeus Quintus | The Maccabian Militia are a capable fighting force, possessing a proud military tradition which can be traced back to the Angevin Crusade. Their finest warriors are often chosen to serve in the ranks of the Maccabian Janissaries Imperial Guard regiment. |
| Tartarus Planetary Defence Force | Tartarus | The Tartarus PDF defended their homeworld when it was besieged by Orks sometime during the 41st Millennium. At one point during this conflict, multiple different factions clashed on the planet which included the Orks, the regiments of the Imperial Guard, the Chaos Space Marines of the Alpha Legion, the Eldar of the Biel-tan Craftworld, and the Space Marines of the Blood Ravens Chapter. |
| Vervun Primary | Verghast | Defended their homeworld of Verghast, during the Sabbat Worlds Crusade against the Forces of Chaos. |
| Ultramar Auxilia | Ultramar |
Sources
- Codex: Armageddon (3rd Edition), pg. 2
- Codex: Eye of Terror (3rd Edition), pg.24
- Codex: Imperial Guard (4th Edition)
- Codex: Tyranids (5th Edition), pg. 13
- Only War: Core Rulebook pg. 50
- Battle of the Fang (Novel)
- Nightbringer (Novel) by Graham McNeill
- Necropolis (Novel) by Dan Abnett
- Cain's Last Stand by Sandy Mitchell
- For the Emperor (Novel) by Sandy Mitchell
- Death or Glory (Novel) by Sandy Mitchell
- The Chapter's Due (Novel) by Graham McNeill
- Games Workshop: Swordwind Pt. 3, The Baran War