Chapter 2: Horus Heresy
When it was noted that Horus had started a rebel against the Emperor Salamanders were one of the seven legions to be sent to confront the fallen Primarch. Umbra's Squad wasn't taken to Istvaan as they were on a misson on a distant planet. As such they survived the Istavaan V massacre only to be coming back to their home planet to meet with most of the legion destroyed. Umbra actully was ready to go to aid the Emperor in Terra, but Vulcan couldn't leave with his Legion at that size. The war mostly ended in Terra with Horus dead and Emperor taken to the Golden Throne. Then it was desided to brake the legions into smaller Chapters. Umbra saw his moment there and made it sure that he would start a new Chapter apart from Salamanders. Umbra toke roughly 400 marines from Salamanders to form Green Shadows Chapter and they moved to a world on the far reaches of Imperial Space. It was only marginally populated and soon it had a fortress of Green Shadows up.