The Defenders of Man is an anti-Dominion terrorist organization. They are the main antagonists of Starcraft 2: Nova Covert Ops. Their stated intentions are to defend humanity from alien threats, such as the Zerg and Protoss. The reality, however, is that they were actually formed to undermine the rule of Emperor Valerian Mengsk. Their founder, General Carolina Davis, was a loyal supporter of Valerian's father, the late Emperor Arcturus Mengsk, and believed that Valerian was weak and not fit to be Emperor. The Defenders of Man would plant psi-emitters on populated Terrans worlds to lure the Zerg, then come in and save the civilians, thereby painting Valerian and the Dominion as ineffective.
At some point, they came into conflict with the Tal'darim by attacking one of their outposts and leaving before the Death Fleet could respond. This prompted the Tal'darim Highlord, Alarak, to attempt to eradicate the Defenders.