Recent reports that Moscow is deploying Cossack groups along the Russian-Ukrainian border near the Kharkiv, Sumy and Chernihiv regions of Ukraine are extremely worrisome, as the Kremlin ostensibly used similar units in its initial invasion of southeastern Ukraine in 2014. Such revelations may presage a new Russian move against Ukraine and be intended as an attempt to muddy the waters about who is behind any aggression. But at the same time, they are the latest sign that the Kremlin wants to have groups with which it can maintain a certain plausible deniability when engaging in destabilizing or aggressive operations both internationally and within the Russian Federation.