A month ago, when Ukraine’s old regime was just starting to crack under the pressure of a revolution, few people in the country had ever heard of Sergei Aksyonov. He was then a marginal figure even in the local politics of the region of Crimea. His Russian Unity party had only three seats in the regional legislature and no representation anywhere else. But that has not stopped him from taking charge. In late January, as the protesters in Kiev began seizing government buildings, Aksyonov started to form an army on the Crimean peninsula. Now he is the de facto leader of the entire region, a post that has thrust him into the center of the most dire political crisis Europe has confronted in years.

From the beginning, the stated aim of his paramilitary force was to defend against the revolutionary wave that was sweeping across Ukraine and, ultimately, to break away from the country entirely. Its first battalion of 700 men came from the youth group of Aksyonov’s political party, and as he continued calling in the proceeding weeks for a “full scale mobilization,” hundreds of others joined his Crimean self-defense brigades. By Feb. 21, the day the Kiev uprising toppled the Ukrainian government, Aksyonov was in command of several thousand troops. “All of them,” he says, “answer to me.”

His rise to power has made him a valuable ally to Moscow and a serious threat to Ukraine and its Western partners. His written appeal to Russian President Vladimir Putin is what opened the door for the Russian occupation of Crimea at the beginning of this month, and on March 4, Putin recognized Aksyonov as the legitimate leader of Crimea, apparently without ever having met the man.