Planetary Defence Force

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.