On December 5, 1994, in Budapest, Ukraine, Russia, USA and UK sign the Budapest Memorandum, one of the most important documents for post-Cold War European security.
Context: Ukraine, after independence from USSR in 1991, inherits the world's third-largest nuclear arsenal (approximately 1,900 strategic nuclear warheads and 2,500 tactical nuclear weapons).
Participants: Ukraine (Leonid Kuchma), Russia (Boris Yeltsin), USA (Bill Clinton), UK (John Major).
Agreements:
1. Ukraine renounces nuclear arsenal and transfers all weapons to Russia
2. Russia, USA and UK guarantee Ukraine's territorial integrity and independence
3. They commit not to use force or threats against Ukraine
4. No economic pressure to influence Ukrainian policy
Implementation: By 1996, Ukraine transfers all nuclear weapons to Russia. Becomes non-nuclear state.
Violation: On February 20, 2014, Russia annexes Crimea, directly violating guarantees. On February 24, 2022, full-scale invasion begins, completely demolishing the memorandum. Ukraine, denuclearized in exchange for security guarantees, finds itself invaded precisely by those who had guaranteed its security.