As Russia helps itself to Crimea, some Ukrainians are wishing they had a nuclear deterrent against Vladimir Putin’s territorial ambitions. Ukraine had a vast nuclear arsenal once, after all, which it gave up 20 years ago.  Now the country may be second-guessing that decision—and even contemplating whether to reverse it.  “[T]here’s a strong sentiment in Ukraine that we made a big mistake,” Pavlo Rizanenko, a member of Ukraine’s parliament, told USA Today this week. “In the future, no matter how the situation is resolved in Crimea, we need a much stronger Ukraine. If you have nuclear weapons people don’t invade you.”  That rhetoric startled foreign policy insiders in Washington. One former Obama administration official says he can’t recall hearing a Ukrainian official publicly regret the country’s denuclearization before.  But Rizanenko’s thinking isn’t unique. “Russia would not invade a nuclear state,” the controversial former president of Georgia, Mikheil Saakashvili, said in an interview with TIME last week. Saakashvili, whose own country fought a territorial dispute with Putin in 2004, lived in Ukraine for several years and maintains deep political ties there. “Ukraine could still make a bomb,” he said.  In theory, that’s true. But experts say it would be a long and contentious road. Ukraine lacks suitable nuclear material and the means to produce it. Going nuclear would also bring down harsh reprisals from both Russia and the West.  Ukraine “does not have a plausible near-term scenario for developing nuclear weapons,” says Gary Samore, the former coordinator for weapons of mass destruction on President Barack Obama’s National Security Council.  “Over the long term, if they made a major national decision, they would have the capability” to develop nuclear weapons, says Matthew Bunn, a non-proliferation expert at Harvard’s John F. Kennedy School of Government. But, he adds, “there would be a lot of chances for Russia and the United States to lean on them before it reached fruition.”  Obama administration officials aren’t sweating the prospect. Speaking at a nuclear security conference in Washington Tuesday, Samore’s White House successor, Elizabeth Sherwood-Randall, praised the Ukrainians as “important leaders in nuclear nonproliferation. … They have truly been trailblazers.”  “We fully anticipate that Ukraine will remain a leader in this field,” Sherwood-Randall added.  Any move by Ukraine to reacquire nuclear weapons would reverse what may be history’s most dramatic voluntary surrender of military capability. For a brief moment after the fall of the Soviet Union, Ukraine had the world’s third-largest nuclear arsenal—some 1,900 weapons, most of them long-range cruise missiles. Three year’s after the USSR’s 1991 collapse, which left Ukraine an independent state, the country signed an agreement with the U.S., Great Britain and Russia known as the Budapest Memorandum, under which it agreed to ship the warheads on its territory to Russia for elimination.  Ukraine’s then-president Leonid Kravchuk cast the decision in idealistic terms, saying it would lead the world toward “disarmament and for the elimination of nuclear weapons.” But he also had more pragmatic motives. The move earned yielded goodwill from the U.S., which linked the surrender to help from the World Bank, the IMF and NATO (it also meant a quick cash infusion from the sale of nuclear material—rendered unusable for bombs—from the dismantled weapons).  Members of Ukraine’s parliament protested, calling nukes a crucial shield against Russia’s territorial ambitions—which were plenty clear even then: In July 1993, Russia’s legislature had voted unanimously to confirm the “Russian federal status” of the Crimean city of Sevastopol, leading Ukraine to appeal to the United Nations.  Russia backed down. But through the Budapest Memorandum, Ukraine insisted on and won assurances of respect for its sovereignty and borders. Specifically, the parties pledged to “seek immediate United Nations Security Council action… if Ukraine should become a victim of an act of aggression.”  That language counts for little, however, when the aggressor is Russia—which wields veto power on the Security Council—and when Putin argues that the Budapest agreement is obsolete anyway. On March 4, the Russian president described post-revolutionary Ukraine as “a new state,” one “with which we have signed no binding agreements” (never mind that Putin also calls Kiev’s new government illegitimate).  In a closed-door Capitol Hill briefing from members of Congress on Tuesday, Obama administration officials were pressed about the ominous precedent of seeing the violation of a state that relinquished nuclear arms in return for security guarantees. Colorado Republican Rep. Doug Lamborn asked assistant Secretary of State for European and Eurasian Affairs Victoria Nuland why the U.S. hasn’t done more to enforce the Budapest Memorandum against Putin’s Crimean annexation.  “She said it was a political treaty, not a NATO-type binding treaty, and so you make political noises and objections and that’s all you can do,” Lamborn told TIME after the briefing.  Given all that, it’s not hard to see why Ukrainians might want to revert to pre-Budapest days themselves and go nuclear again.  Ukraine does have some highly trained scientists from the former Soviet nuclear complex, including, according to Bunn, Vyacheslav Danilenko, an implosion systems designer who has been linked to Iran’s nuclear program. What it lacks is nuclear material.  That wasn’t the case just a few years ago. When Obama took office, Ukraine still had enough highly enriched uranium (HEU)—in the form of fuel for scientific research reactors—to build several nuclear weapons. But in a signature achievement of Obama’s drive to enhance global nuclear security, Kiev agreed to give up that material as well. The last of Ukraine’s HEU was shipped out of the country in March 2012—one reason Sherwood-Randall dubbed the Ukrainians nonproliferation “leaders” and “trailblazers.”  Today, Ukraine operates several civilian nuclear reactors, but lacks a reprocessing facility to enhance its reactor fuel to bomb-grade quality. The country does possess natural uranium, but not the centrifuges needed for its enrichment. “In theory, Ukraine could develop an indigenous capability to produce fissile material,” Samore says. “But it would take many years.”  Too long to save Crimea. But long enough for severe condemnation and retribution—both from a threatened and dangerous Russia and an American president who considers nuclear nonproliferation one of his most important priorities. A nuclear Ukraine isn’t impossible, but it’s almost certainly not going to happen.  -with reporting from Alex Rogers in Washington
Despite calls in Kiev to develop a nuclear deterrent against Vladimir Putin's Russia, experts say the idea is far-fetched. Building a bomb would be incredibly difficult and contradicts the country's past efforts for nuclear nonproliferation