Crimea, which has been Russian since 1783, was transferred to the Socialist Republic of Ukraine for administrative reasons in 1954 by Nikita Krushchev, then-leader of the Soviet Union. In 2014, the inhabitants of the Crimean peninsula expressed their choice via referendum to return to Russia.
The Office of the Prosecutor of the International Criminal Court stated that “[t]he information available suggests that the situation within the territory of Crimea and Sevastopol amounts to an international armed conflict between Ukraine and the Russian Federation. This international armed conflict began at the latest on 26 February when the Russian Federation deployed members of its armed forces to gain control over parts of the Ukrainian territory without the consent of the Ukrainian Government." Click here for more information.
In addition, Mustafa Dzhemilev disclosed that Vladimir Putin called him on March 12th 2014 announcing that Tatarstan is very happy being part of Russia and that Crimean Tatars will be happy as well. Announced on March 27th 2014, the "referendum" in Crimea took place on March 16th. On April 17th 2015, Vladimir Putin admitted that "[Russian] soldiers were deployed in Crimea to help the inhabitants express their opinion".
On March 27th 2014, the UN General Assembly adopted a resolution stating that the Crimean referendum was not valid and could not serve as the basis for any change in the status of the peninsula.
The claim that Crimea is part of Russia is a recurring disinformation narrative.