March 9, 2022—Editor’s Note: When searching for solutions when one country attacks another, it’s helpful to look back in history and seek guidance from international agreements that are relevant. This article is the first in a series to help readers understand the background of Ukraine’s security situation and international expectations.
On January 11, 1994, Ukraine agreed to give up its vast nuclear arsenal in exchange for security guarantees. Later that year, Ukraine signed the Budapest Memorandum on Security Assurances with Russia, the United States and the United Kingdom. At the time, Ukraine held 176 intercontinental missiles armed with some 1,240 nuclear warheads and 592 nuclear warheads aboard bombers. Following the agreement, Ukraine dismantled and destroyed the arsenal.
After Ukraine agreed to give up its nuclear weapons, U.S. President Clinton, Russian President Boris Yeltsin, and Ukrainian President Leonid Kravchuk met in Moscow, signing a Trilateral Statement on January 14, 1994. It preceded the Budapest Memorandum. 
On Dec. 5, 1994, Presidents Yeltsin, Clinton and Kuchma and UK Prime Minister John Major signed the Budapest Memorandum.
What is the difference between a memorandum and a treaty?
A Memorandum of Understanding, or MOU, is an agreement between two or more parties. Memorandums are not legally enforceable, but facilitate the exchange of information among parties.
In contrast, a treaty is legally enforceable under international law. They include two types: a bilateral treaty in which two countries or parties make an agreement; and a multi-lateral which is among three or more countries. The main difference between a memorandum and a treaty is that one legally enforceable (treaty) while the other is not.
What is the 1994 Budapest Memorandum?
The 1994 Budapest Memorandum, also called the “Memorandum on Security Assurances,” is an agreement that Ukraine will reduce its nuclear weapons arsenal to zero within a defined period of time and that all countries part of the memorandum will respect the borders and sovereignty of Ukraine.
Signatories agreed “to respect the independence and sovereignty and the existing borders of Ukraine.”
Additionally, signatory countries provided security assurances absence a commitment of military forces should Ukraine become a future target of aggression.
What countries are part of it?
Signatory countries of the 1994 Budapest Memorandum are Russia, Ukraine, the United Kingdom, and the United States.
Which parties have honored or otherwise lived up to their commitments in the MOU?
Ukraine fulfilled its commitment to the Budapest Memorandum by disarming its nuclear weapons and joining the Treaty on the Non-Proliferation of Nuclear Weapons.
Russia has not fulfilled its commitments outlined in the Budapest Memorandum. Specifically, Russia violated the agreement by failing to respect the independence, sovereignty, and borders of Ukraine as demonstrated by its 2014 incursion into the Crimean Peninsula and the ongoing invasion of Ukraine that started in February 2022.
The United States and the United Kingdom fulfilled their commitments outlined in the Budapest Memorandum. During negotiations, Ukraine voiced concern about the possibility that Russia could violate the agreement. And U.S. officials promised to “take a strong interest and response.” Based on current economic sanctions enacted and military aid provided, the aforementioned signatories are meeting their obligations under the MOU.
Editor’s Note: It can be argued that the United States and the United Kingdom should do more to guarantee Ukraine’s security. Ukrainian President Volodymyr Zelensky is making that case. And the point is debatable.
Are there consequences for breaking the commitments?
As a memorandum of understanding is non-binding, there are no legal consequences. However, the signers agreed to act in the case of a violation of Ukraine’s sovereignty by taking the case to the UN Security Council.
Today, the United States and the United Kingdom, along with several other countries and the United Nations, are supporting Ukraine through economic sanctions, and military aid.
16-Page Budapest Memorandum
4-Page Letter By Foreign Representatives of Russia, U.K., U.S., and Ukraine
