Through Budapest Memorandum on Security Assurances, Belarus, Kazakhstan and Ukraine gave up their nuclear weapons between 1994 and 1996. According to the same source:
Before that, Ukraine had the world's third largest nuclear weapons stockpile, of which Ukraine had physical if not operational control.
The signatories offered Ukraine "security assurances" in exchange for
its adherence to the Treaty on the Non-Proliferation of Nuclear Weapons.
According to this article, this decision was not a wise one:
"As soon as it declared independence, Ukraine should have been quietly encouraged to fashion its own nuclear deterrent," the University of Chicago scholar wrote in a 1993 Foreign Policy piece. "A nuclear Ukraine ... is imperative to maintain peace between Ukraine and Russia. ... Ukraine cannot defend itself against a nuclear-armed Russia with conventional weapons, and no state, including the United States, is going to extend to it a meaningful security guarantee."
Question: why did Ukraine apparently give up the nuclear weapons so easily? What did it gain to counterbalance giving up to such a strategic advantage?
It is undeniable that the West levied formidable pressure on Ukraine to dissuade it from holding onto its nuclear weapons. It is also undeniable that the nuclear disarmament of the post-Soviet successor states came at a low cost for the West […]
Yet it must be acknowledged that, ultimately, Ukraine surrendered its nuclear weapons not because of Western pressure or of the things it thought it got in exchange, but because of the country it wanted to be: part of Europe and of the community of nations that are bound by common rules and values. — "Was Ukraine’s nuclear disarmament a blunder?" by EuroMaidan Press
Here are some outstanding reasons:
- As of 1991, the nuclear disarmament of Ukraine was considered a part of the nuclear disarmament of the falling Russia's "USSR". Having a nuclear Ukraine on the world map would undermine the post-Yalta security order, as I mentioned in another answer;
- Ukraine used to have weak control over its Armed forces. Virtually all control and commandment was Russian; acting FSB/KGB generals took the key positions in Ukraine's Ministry of Defense and Security Service. This was the case till the moment of Revolution of Dignity in 2014;
Weak control over the Strategic Nuclear Forces: the security codes, wires, and communications were Russian-designed and Russia-controlled:
While Ukraine had physical control of the weapons, it did not have operational control, as they were dependent on Russian-controlled electronic Permissive Action Links and the Russian command and control system. — Wikipedia and its relevant links
Sky-high organized crime with the Russian origins made Ukraine a threat, because a relatively small group of corrupted officials jointly with criminals could capture the nuclear weapons or, most dangerously, some radioactive materials;
The fears above are expressed well in George H. W. Bush Chicken Kiev speech (1991), three years before the Budapest Memorandum has been signed. The Bush speech was criticized by Ukrainians for its fear of Ukraine's liberation, and the very reason why Bush cautioned against "suicidal nationalism" is that the U.S. government did not believe that Ukraine can control its sovereignty, in general and it nuclear arsenal, in particular.
- "Some 1,900 strategic nuclear warheads that had been designed to attack the United States". Arguably, it was seen too difficult to re-configure the weapons against another enemy, hence, reducing its capability to help the national security of Ukraine;
- Maintenance of 1,900 warheads is expensive. The cost of maintenance the nuclear arsenal of Ukraine was estimated to $5 billion per year, in prices of 1993. Note that Ukraine did have trained staff, factories, equipment, and infrastructure. Even having the expendable materials manufactured in Ukraine, the factories were tightly linked with the Russian ones;
"Kiev did this on the condition that it receive security guarantees or assurances." — Steven Pifer
Ukraine chose security guarantees over being a threat. It could be seen a wise action before it appeared that the "guarantees" do not guarantee the Ukraine's territorial integrity.