Ukraine is an independent nation in Eastern Europe and a former republic of the Soviet Union. In 1954, Soviet Premier Nikita Khrushchev transferred Crimea from Russia to Ukraine. When the Soviet Union dissolved in 1991, the region remained under Ukrainian control. Ethnic Russians have continued to constitute the majority of Crimeans, despite the cartographical and political delineation.

The territorial transfer is said by commentators of history to have been a gift to mark the three-hundredth anniversary of Ukraine uniting with Russia. The Kremlin cited economic ties between the peninsula and Ukraine as another reason for the transfer, but at the time the region’s major economic engine was tourism from throughout the USSR. The history commentators suggest that part of the real reason for the transfer was actually an act of reparation motivated by Khrushchev’s affection for Ukraine and the Stalin-induced famine that had plagued the country two decades earlier.

Ukraine had nuclear weapons placed in its territory by the Kremlin during the Soviet era. In 1994, it agreed [PDF] to give these nuclear weapons to Russia as terms of the Budapest Memorandum in exchange for a covenant by the US, UK and Russia to keep the nation’s current borders.

Ukraine was the Soviet Union’s most populous republic aside from Russia. When more than 90% of Ukrainians voted for independence in 1991, it entailed the end of the USSR. In Crimea, the vote for independence was more than 50%. Considering the ethnic makeup of Crimea, this means some ethnic Russians voted for independence as well. The Soviet leader at the time, Mikhail Gorbachev, tried to join Russia, Ukraine, and other former Soviet republics in a more decentralized union. The new leaders of Russia and Ukraine, Boris Yeltsin and Leonid Kravchuk, declined to join. The two leaders did join their nations to the Commonwealth of Independent States, which serves to promote trade and legal cooperation between the former Soviet republics.

Current Russian President Vladimir Putin actively supports former Ukrainian President Viktor Yanukovych, who was ousted by pro-European protesters in February 2014. Yanukovych was elected president in 2010 and fled to Russia following his fall from power. During his reign, allies of Yanukovych took up leadership positions in Crimea while the Kremlin funded pro-Russian groups in the region. Once Yanukovych fell, these groups organized militia forces to defend Crimea from pro-European Ukraine. Yanukovych maintains he is still the president of Ukraine.

Russian laws allow the Russian military to deploy in foreign nations to protect ethnic Russians. On March 1, 2014, the Russian parliament granted President Putin authority to deploy Russian forces not only in Crimea but all of Ukraine. At the same time, thousands of unmarked Russian-speaking troops appeared all throughout Crimea and particularly around Ukrainian military installations. The Kremlin denies that the forces are Russian military and claims the troops are members of pro-Russian militias. Western commentators say the forces bare contemporary Russian military equipment and are too well-organized to be militia forces.

On March 6, 2014, a week after the pro-Russian forces commandeered government buildings, Crimea’s parliament voted to join Russia and set a referendum for the approval of Crimeans. The referendum was held ten days later on March 16. The result was a 97% vote in favor of joining Russia. The West refuses to recognize the referendum and has deemed it illegitimate. Russia formally annexed Crimea on March 18, 2014.

The 2008 Russian invasion of another former Soviet republic, Georgia, bares similarities to the 2014 Russian involvement in Crimea. Like with Crimea, the Kremlin asserted that it had an interest in protecting ethnic Russians. Military conflict ensued after Russian forces entered Georgia. The result was and continues to be de facto Russian control of the pro-Russian autonomous Georgia regions of Abkhazia and South Ossetia. This roughly amounted to a 20% territorial loss for Georgia.