See Historical Precedent
Kiheitai 鬼兵隊 literally means "Army of Demon Soldiers". Resurrected from the 義勇軍 gi yuu gun (volunteer army) from the Joui Wars, this is an extremist group that stops at nothing in its mission to 'destroy the world', quoting the leader Takasugi Shinsuke 高杉 晋助.
From mass-producing bio-mechanical swords for their fighters, causing internal strife within the Shinsengumi 真選組 in order to wipe them out, to collaborating with the space pirate group Harusame 春雨, this violent group stops at nothing to destabilize the world. Leader Takasugi Shinsuke even offered his Joui War comrades' heads to secure assistance from Harusame 春雨, namely Katsura Kotarou and Sakata Gintoki, as he explained in Episode 61.