This article considers Baltic defence strategically, focusing on three scenarios of Russian aggression against the Baltic states: 1) an ambiguous invasion, what the West would call a hybrid war; 2) a hasty invasion by Russian formations already in and around the Baltic region; and 3) a prepared invasion by more substantial Russian forces brought within striking distance of the Baltic states from other parts of Russia. The ultimate question for each is: does this particular scenario present Russia with a viable strategy, a convincing theory of success? Each scenario is explored through the perspectives of military practice or tactics, then politics, and then synthesized through a strategic perspective. The article argues that neither the ambiguous invasion nor the hasty invasion scenarios provide convincing theories of success for Russia, whereas the prepared invasion does provide a compelling theory of victory.