Officially formed during the development of the Helian system in the Old Federal Era, long before the Imperial Annexation of the Angel Reach in 4404 A.D., the HPDF has a long and proud history of providing planetary security to Helian interests within the system. The HPDF is officially composed of regular units trained from the Helian population as a standing, professional military unit, but many divisions are significantly augmented by paramilitary forces and freelance units under contract by the Helian government.

By the time of the annexation of ISAR in 4404, the HPDF was the largest independent surface military known to exist, and made up more than sixty percent of the combat-ready planetary forces of the ISAR federation. Under the Imperial Flag, the HPDF remains a semi-independent military structure; as Imperial military commanders recognised its effectiveness, especially to reduce the need for Imperial Planetary Forces to garrison the edge-worlds in the Angel Reach. The HPDF is officially a sub-branch military operating under the command of the Planetary Forces Division of the Angel Sector Fleet of the Aquarian Imperial Navy, but enjoys almost complete autonomy within Imperial Compliance.

The HPDF mostly operates aging CEG-era equipment, though some of it has been extensively upgraded by ISAR corporations such as Rockal Armaments before the Annexation of the Reach. These updates essentially brough the equipment standard of the HPDF to near-peer with the Old Federal Planetary Forces, but still significantly lagging behind the technology standard of the Aquarian Imperial Military. After the annexation, there had been plans to acquire updated Imperial technology for the HPDF but so far the Imperial Military has been reluctant to provide even obsolete inventory. However, the economic boom brought in by the annexation has allowed the HPDF to source higher quality independently built vehicles and equipment for its troops, maintaining the Force as the Angel Reach (and likely beyond)'s foremost non-Imperial surface military power; more than sufficient to prevent any brazen raiding parties by remnants of the pirate cartels lurking in the nearby Angel Nebula.