Violent conflict in Ukraine, both in Crimea and the Donbas region of eastern Ukraine, has presented a significant challenge for international security. Ukraine was the second largest, after Russia, of the 15 “union republics” of the Soviet Union that became independent and sovereign states in late 1991. That sovereignty seemed to have been guaranteed when Ukraine was admitted into the United Nations (UN) and the Organization for Security and Cooperation in Europe (OSCE) in 1992 within its post-Soviet borders. Ukraine’s status was further assured in the Budapest Memorandum of 1994, when the United States, France, the United Kingdom and the Russian Federation acknowledged Ukraine’s sovereignty within its 1994 borders in exchange for Ukraine’s turning its nuclear warheads over to Russia and joining the Nuclear Non-Proliferation Treaty as a non-nuclear weapons state. These recognized borders of Ukraine included the peninsula of Crimea that had been transferred from the Russian Federation to Ukraine in 1954.
Panyan, Karina. 2017. “Blockade of Peace: Corruption and Crime.” In Understanding the 'Hybrid' Conflicts in Ukraine, Washington, D.C.: Johns Hopkins University. essay, 93–103. http://www.sais-jhu.edu/sites/default/files/Ukraine%20Master%20Doc%20May%2013%20June.pdf