While it may be a small naval branch, they get the job done.
The 405th for it's earliest years rode with the 182nd naval divison, the naval branch of the macronian 255th. The 405th and the 182nd were happy with this, but there was still a lot to be desired. After countless pleas from the 255th/182nd's commissar, the 222nd was born.
It was at the blockade of the planet of Terglint that the 222nd naval division finally showed their worth, while the 405th were on the planet assisting some Cadians in distress, the 222nd fought off a Dark Eldar fleet that was twice their own size. the Eldar were attempting to assist some heretic forces on the planet, but thanks to the efforts of the 222nd the Dark Eldar were thwarted, and the rebellion put down.
Recently, due to failed Imperium attempts to save Fesce from Chaos infection the 222nd was orderred to launch an orbital barrage which would strategically hinder Chaos forces in that solar system and the surrounding solar systems as Fesce was a regional hub for Chaos, on the planet rebellious forces had attempted to regain freedom, all in vain. but the 222nd assisted the 405th in relocating the Chaos-rebelling forces.