At the time of the Soviet Union's collapse in 1991, Ukraine became the third-largest nuclear power in the world, trailing only the United States and Russia. However, it is important to recognize that Ukraine had Soviet nuclear weapons stationed on its territory, which were controlled by Russia. Russia secretly transported tactical nuclear weapons back to its territory, leaving Ukraine with strategic ballistic missiles armed with nuclear warheads aimed at the U.S. and other NATO countries, as well as strategic bombers designed for long-range missions.

The nuclear weapons in Ukraine were, in reality, under Moscow’s control, as the "nuclear briefcase" was in the hands of the Russian president. Ukraine’s leadership had no access to launch codes and, therefore, had no technical ability to prevent an unauthorized launch of nuclear missiles from its territory. Additionally, maintaining and servicing a nuclear arsenal required substantial financial resources and a highly advanced technological infrastructure. In the early 1990s, Ukraine was in an economic crisis and lacked the means to ensure the proper storage and upkeep of nuclear weapons. The memory of the Chernobyl disaster was still fresh, and there were fears of potential nuclear accidents at missile silos.

The international community was focused on preventing nuclear proliferation. The U.S. and the U.K., in particular, pushed for Ukraine to join the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) as a non-nuclear state. 

By giving up nuclear weapons, Ukraine demonstrated its commitment to peaceful coexistence and strengthened its international reputation. Most importantly, Ukraine received security assurances from nuclear powers. These commitments were formalized in the "Memorandum on Security Assurances in Connection with Ukraine’s Accession to the Treaty on the Non-Proliferation of Nuclear Weapons"—commonly known as the Budapest Memorandum—signed in 1994 by Ukraine, the U.S., the U.K., and Russia. In Ukraine, these commitments were interpreted as legal security guarantees because the Ukrainian and Russian versions of the document used the word "guarantees" , while the English version used the word "assurances".

This difference in wording later became a key issue after Russia grossly violated the agreement by annexing Crimea and occupying parts of eastern Ukraine. The responsibilities of the U.S. and the U.K. under the memorandum—whether as guarantees or mere assurances — became the subject of heated debate. Russia’s war against Ukraine has exposed the limitations of international security assurances when they lack clear enforcement mechanisms.

Thus, Ukraine’s decision to give up its nuclear weapons was influenced by a combination of internal and external factors, including the lack of real control over its nuclear arsenal, economic and technical constraints, international pressure, and aspirations for global integration. While the decision seemed justified at the time, later events revealed the country’s vulnerability to external threats and the weaknesses of the security assurances it received.