In both Crimea and the subsequent fighting in the Donbas region of Ukraine, Russia’s signature tactic has been the use of so-called “Green Men,” soldiers without identifying insignia whose identity as Russian soldiers the Kremlin denied. Ukraine, Georgia, and even NATO members like Estonia now fear that they could be the next target for Russia’s Green Men. NATO, alarmed by the need to prepare for this unexpected tactic, has committed to develop new countermeasures to defend against this threat. Green Men, or deniable forces, are a central part of what has come to be called “hybrid warfare” in the “gray zone” between war and peace. All of this seems to be a new and innovative departure from traditional tactics, perhaps even a new model for conflict in the 21st century.
However, deniable forces are nothing new. Nor, in fact, is the specific phenomenon of using them to seize a piece of territory, as Russia did in Crimea. There is a long history of hybrid warfare in general and of intervening with deniable forces in particular. This history points not just to the enduring nature of the threat, but also to the contours of a “counter-hybrid” strategy to defeat it.