Soviet leader Nikita Khrushchev transferred Crimea from Russia to Ukraine in 1954, when both were part of the USSR, to commemorate the 300th anniversary of the unification of Moscow and Kyiv. In 1991, when the Soviet Union collapsed, the peninsula became part of newly independent Ukraine.

The Kremlin said it reserves the right to use nuclear weapons if it faces aggression by Western countries. Overnight, Moscow attacked Kyiv, killing at least eight people.