The Budapest Memorandum on Security Assurances comprises three substantially identical political agreements signed at the OSCE conference in Budapest, Hungary, on 5 December 1994, to provide security assurances by its signatories relating to the accession of Belarus, Kazakhstan and Ukraine to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).

The protocol committed Belarus, Kazakhstan and Ukraine to adhere to the NPT as non-nuclear weapons states as soon as possible.

Later in 1993, the Ukrainian and Russian governments signed a series of bilateral agreements giving up Ukrainian claims to the nuclear weapons and the Black Sea Fleet, in return for $2.5 billion of gas and oil debt cancellation and future supplies of fuel for its nuclear power reactors.

[4] On 18 November 1993, the Rada passed a motion agreeing to START I but renouncing the Lisbon Protocol, suggesting Ukraine would only decommission 36% of missile launchers and 42% of the warheads on its territory, and demanded financial compensation for the tactical nuclear weapons removed in 1992.

[21] In 2009, Russia and the United States released a joint statement that the memorandum's security assurances would still be respected after the expiration of the START Treaty.

[24] The troops were attached to the Russian Black Sea Fleet stationed in Crimea,[25] which placed Russia in violation of the Budapest Memorandum.

The Russian Foreign Ministry had initially denied the movement of armoured units attached to the Black Sea Fleet in Crimea which led to the troops being labelled "little green men",[26] however after taking full military control over Crimea Russia finally did admit their involvement but asserted that they were acting within the scope of the various agreements between the two countries.

Russia responded by staging a so-called "illegal referendum" on whether the Crimea should join it, where the option to remain part of Ukraine and keep the same rights and laws of 2014, as before, was not present.

Prior to the referendum Russian military blocked all the opposition TV and media as well as radically put down the rallies for support of Ukraine.

After the annexation of Crimea by Russia in 2014, Canada,[27] France, Germany, Italy, Japan,[28] the UK,[29] and the US[30][31] stated that Russian involvement was a breach of its Budapest Memorandum obligations to Ukraine and in violation of Ukrainian sovereignty and territorial integrity.

[35] On 24 March, Canadian Prime Minister Stephen Harper led the G7 partners in an ad hoc meeting during the 2014 Nuclear Security Summit for a partial suspension of Russian membership from the G8 due to Russia's breach of the Budapest Memorandum.

By breaching that assurance, President Putin has provided a rationale for those elsewhere who needed little more than that already furnished by pride or grievance to arm themselves to the teeth."

"[37] However, Canadian journalist Michael Colborne pointed out that "there are actually six obligations in the Budapest Memorandum, and the first of them is 'to respect the independence and sovereignty and the existing borders of Ukraine'".

Steven Pifer, an American diplomat who was involved in drafting the Budapest Memorandum, later commented on "the mendacity of Russian diplomacy and its contempt for international opinion when the foreign minister says something that can be proven wrong with less than 30 seconds of Google fact-checking?

[42][43][44] In 2008 and 2011, Putin expressed the opinion that neither the transfer of Crimea to Ukraine nor the Budapest Memorandum signed by Yeltsin were binding for Russia.

[45] Ukrainian President Volodymyr Zelenskyy has publicly commented on the Budapest Memorandum by arguing that it provides no true guarantee of safety due to Russia's coercive power.

If they do not happen again or their results do not guarantee security for our country, Ukraine will have every right to believe that the Budapest Memorandum is not working and all the package decisions of 1994 are in doubt.

[2][51] According to Stephen MacFarlane, a professor of international relations, "It gives signatories justification if they take action, but it does not force anyone to act in Ukraine.

[52] Whether or not the memorandum sets out legal obligations, the difficulties that Ukraine has encountered since early 2014 may cast doubt on the credibility of future security assurances that are offered in exchange for nonproliferation commitments.

He added that in retrospect, American and Ukrainian officials did not foresee the Russo-Ukrainian War and because of that Ukraine was willing to accept security "assurances" from the U.S. and Britain, which unlike "guarantees," do not require the use of military force if the agreement was violated.