After the military intervention in Ukraine in 2014, and the swift, bloodless annexation of Crimea, the international community recognized Russia as an expert on hybrid warfare. However, the ongoing conflict in Donbas unleashed by Moscow during the second less successful hybrid campaign remains a sore point not only for Ukraine but also for Russia which has to cope with costly consequences in order not to lose in the East of Ukraine and more importantly in its undeclared war on the West. This thesis conducts a comparative analysis of two Russian hybrid warfare models: (1) in Crimea; (2) in Eastern Ukraine, and focuses on the following research questions: Why was the Russian hybrid warfare in Crimea more successful than in Donbas? What measures can the state take to improve its ability to face hybrid attacks? The findings reveal that despite the presence of a set of common factors, the different degrees of success and outcomes of both cases are attributable to the fact that successfully employing the full spectrum of hybrid warfare, is actually bound not only to a number of prerequisites but also with specific favorable features of the conflict zone and several critical elements. While hybrid tactics vary depending on country and region, it is built on exploiting the enemy's vulnerabilities, the...