Budapest Memorandum on Security Assurances is an international treaty signed on 5 February 1994 in the Hungarian capital Budapest by Ukraine, the United States of America, Russia, and the United Kingdom concerning the nuclear disarmament of Ukraine and its security relationship with the signatory countries. According to the memorandum, Russia, the USA, and the UK confirmed, in recognition of Ukraine becoming party to the Treaty on the Non-Proliferation of Nuclear Weapons and in effect abandoning its nuclear arsenal to Russia, that they would:
In February 2014, unidentified troops seized or blockaded various airports, as well as other strategic sites throughout Crimea. Official Ukrainian sources have said that the troops are Russian, attached to the Russian Black Sea Fleet stationed in Crimea, likely placing Russia in violation of the Budapest Memorandum. The Russian Foreign Ministry has confirmed the movement of armoured units attached to the Black Sea Fleet in Crimea, but asserts they are acting within the scope of the various agreements between the two countries, and other official Russian sources deny that the units in the area of Sevastopol International Airport, specifically, are attached to the Black Sea Fleet.
In response to the crisis, the Ukrainian parliament has requested the Memorandum's signatories reaffirm their commitment to the principles enshrined in the treaty, and further asked that they hold consultations with Ukraine to ease tensions.