Juno also maintains a Planetary Defence Force to protect the planet against both external invasion and internal uprising. The Grand Army of the Sovereign, also known simply as the Grand Army or colloquially as the Oldbloods, is imbued with many millennia of tradition, pomp, and grandeur. It has a standing force of several million troops, the majority infantry but including other types from shock cavalry to heavy artillery. Its members are possessed of a fearsome esprit de corps, and many companies are tithed en masse to the world’s Astra Militarum regiments such as the Juno Grand Fusiliers , where they "find glory across the sector and beyond".
Members wear a distinctive gold-chased cuirass wrought with all manner of ornate texts and traceries, complemented by a spiked helm, tan britches, and sleeves of deepest royal purple. The officers’ uniforms are still more refined, with mantles of rare fur and pelisse jackets, resplendent with gleaming golden buttons and braided fasteners. Though the Oldbloods might be mistaken for mere ceremonial troops intended more for showy displays of power than actual combat, "nothing could be further from the truth". The Grand Army is highly experienced, its units bearing the brunt of the "near constant purges" of the ruined wastes in order to cull the populations of mutants and recidivists that lurk within. Furthermore, because the world has been invaded so many times throughout its long history, the Grand Army has developed a deeply ingrained institutional memory. It has at some point in the past fought against almost every enemy of Mankind, and retains much of the knowledge on how to do so again.
"Despite its splendour and status", the Grand Army is regarded with deep contempt by the average member of the citizenry of Juno. Oldbloods are often used to bolster the Vigil when large scale civil disorder threatens the status quo. With the world and the sector at large experiencing a slow, inexorable slide into damnation and anarchy, instances of such disorder grow ever more frequent, and the Grand Army has recently engaged in several pitched battles against large, armed groups of rebels in the depths of the ruin-strewn wastes.