"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. Ukrainian nuclear weapons are the only reliable deterrent to Russian aggression."
These are the words of John Mearsheimer, one of the most reputed international relations theorists of the 20th Century.
He articulated this argument, however, way back in 1993, for the journal Foreign Affairs, in a paper titled, "The Case for a Ukrainian Nuclear Deterrent".
Mearsheimer wrote this at a time when Ukraine, Russia, the US, and certain European countries were trying to reach agreements on the Kyiv's nuclear disarmament.
After all, in the early 1990s, the third largest nuclear power on the planet (after the US and Russia) was Ukraine.
By 1994, however, Ukraine agreed to sign the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and returned all its nuclear warheads to Russia by 1996.
Ukraine's nuclear disarmament two-and-a-half decades ago has become particularly debatable in the backdrop of the current Russia-Ukraine crisis.
Not only did Russian President Vladimir Putin on 21 February choose to recognise Donetsk and Luhansk – as independent from Ukraine, but he also, in an act of naked aggression, sent Russian troops into the two separatist-controlled regions for "peacekeeping".
Why did Ukraine decide to denuclearise? What did it receive in return? Is the country's lack of nuclear capability one of the reasons why it's desperate to join the North Atlantic Treaty Organization (NATO)? And does Ukraine's non-nuclear status embolden Russia?
The Soviet Union's nuclear stockpile at the time of its dissolution was spread over Russia, Belarus, Kazakhstan, and Ukraine.
When Ukraine became independent from the Soviet Union in 1991, it possessed almost 2,000 nuclear warheads along with a significant number of intercontinental ballistic missiles and strategic bombers, according to the Arms Control Association.
The problem was, that the operation control of those weapons, that is, the trigger button, was not in Kyiv, but in Moscow.
The leaders of sovereign Ukraine were divided regarding what to do with its nukes.
Some wanted to follow the path of Belarus and Kazakhstan, and return them to Russia in exchange for being welcomed into the international community. It would also save them the high costs of maintaining nuclear weapons.
Others wanted to keep the nukes and work towards getting operation control, as acquiring that control could serve as a deterrent against future aggressors.
Eventually, Kyiv decided to go for option number one.
In what became the Budapest Memorandum on Security Assurances, Ukraine signed an agreement in 1994 with Russia, the United Kingdom, and the US.
Ukraine sacrificed its nukes in exchange for financial assistance from the US and a guarantee of border security.
It also had to join the NPT and the START (Strategic Arms Reduction Treaty).
One of key features of the Budapest deal was that the countries that are party to it will "respect the independence and sovereignty and the existing borders of Ukraine" and "refrain from the threat or use of force" against its borders.
The same applied to Belarus and Kazakhstan.
In Ukraine's case, however, the Budapest agreement has been outrightly violated by Russia's actions in Donbas in February 2022, almost 28 years after the agreement.
As Andriy Zahorodniuk, a former defence minister of Ukraine lamented, "We gave away the capability for nothing", as quoted in The New York Times.
Why Ukraine Seeks NATO Membership
Ukraine's desperation to enter NATO is linked to what the Budapest Memorandum does not provide to them.
While the agreement stated that Ukrainian sovereignty will be respected, neither the US nor the UK guaranteed to Ukraine a commitment of military force in case of a foreign attack.
NATO members, however, enjoy that privilege.
Article 5 of the treaty, which is the foundation of NATO's collective defence principle, states that "the Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all".
If such an attack does occur against a NATO member, Article 5 adds that all other members are obligated to assist the the victim (and use armed force if necessary), in order to "restore and maintain the security of the North Atlantic area".
In the absence of the credible deterrent that nuclear weapons are, Ukraine has been seeking entry into NATO to get inducted into this sphere of collective defence.
Ukraine Can't Deter Russia From Using Conventional Force
Russia is simply too strong militarily for a non-nuclear Ukraine to get deterred by the latter's threat of conventional military power.
The latest data of the Russian and Ukrainian militaries provided by the Financial Times exemplifies this.
Ukraine has around 2,55,000 active troops and 9,00,000 in reserves, bringing it to a total of 11,55,000.
Russia, on the other hand, has approximately 10,14,000 active troops and 20,00,000 in reserves – a total of 30,14,000.
In terms of aviation, Russia has 1,531 fighter jets in comparison to Ukraine's 67.
Moscow also has 538 attack helicopters, while Kyiv possesses only 34.
Such is also the case with armoured vehicles. Russia has 27,100 of the compared to Ukraine's 11,435. Russia also has 13,000 tanks in comparison to Ukraine's 2,430.
Finally, Russia possesses 214 warships, while Ukraine has 13.
These numbers, that signify drastic differences in the military capabilities of the two countries, would matter less if both were nuclear armed.
After all, it takes only one nuke to cause catastrophic destruction.
The absence of even that one nuke in Ukraine and the obvious superiority in conventional military capabilities have indeed emboldened Moscow to pursue an aggressive policy towards Kyiv.
What has made Russia even more confident is that NATO is not obligated to militarily assist Ukraine under article 5, and that the US has clearly stated that it will not sent "American servicemen to fight Russia in Ukraine".
Whether Ukraine embarks on a journey to reacquire nuclear capability, something that will require assistance from the US and NATO, will become known in the near future.
(With inputs from The Financial Times and The New York Times)