When it comes to the art of discretion in international affairs, the British are without peer. Yet now a Scottish life peer’s loose lips appear to have had a role, if only unwittingly, in escalating tensions between Russian and the West over nuclear weapons of the tactical kind. 

It started on March 20, when a junior British defense minister, 73-year-old Annabelle Goldie, gave in the House of Lords a surprisingly candid parliamentary answer about aid to Ukraine. The baroness said unambiguously that Britain would send “armor-piercing rounds which contain depleted uranium” to Ukraine, adding that the weapons are “highly effective in defeating modern tanks and armored vehicles.”

Depleted uranium is a byproduct of the uranium enrichment process in making nuclear weapons, but while the rounds retain some radioactive properties, they do not generate nuclear reactions like a nuclear weapon would. It is unclear whether Ms. Goldie, who is a longtime Scottish Tory who assumed office during the last days of Boris Johnson’s premiership, was aware of the consequences of her candor.

By March 21, in any event, her comments were rippling across Russian social media, leading President Putin to say that “if all this happens, Russia will have to respond accordingly, given that the West collectively is already beginning to use weapons with a nuclear component.” It did not take the Russian strongman long to make good on his threat, even if the risk posed by it is regarded by most in Washington as overstated.

On Saturday, Mr. Putin announced plans to station tactical nuclear weapons, intended for battlefield use and with short ranges, in neighboring Belarus. According to American estimates, Russia has about 2,000 tactical nuclear weapons including bombs that can be carried by tactical aircraft, warheads for short-range missiles, and artillery rounds. 

The Kremlin said it will have control over the ones it will eventually send to Belarus, though there will be no place to store them until July. Yet the idea of putting tactical nukes in proximity to the Russian aircraft and missiles in Belarus already is raising hackles in Europe and tensions in Ukraine.

That is why on Sunday the Ukrainian government called for an emergency meeting of the UN’s Security Council to counter what it branded “the Kremlin’s nuclear blackmail.” Whether it constitutes a real crisis or just another chapter in the fraying international fabric after more than a year of war in Europe remains to be seen, but Washington, at least for now, is unfazed. 

“We have not seen any reason to adjust our own strategic nuclear posture nor any indications Russia is preparing to use a nuclear weapon,” the National Security Council spokeswoman, Adrienne Watson, said. “We remain committed to the collective defense of the NATO alliance.”

Signs in Belarus also point to a mitigated risk of escalation, despite the unavoidable fact that “uranium” and “nuclear” are among the most loaded pair of words in the English language. For one thing, in 1994, the Belarusian president, Alexander Lukashenko, agreed to cede the strategic nuclear weapons lingering in Belarus since the end of the Cold War. Had he not done so, he would have had to tacitly agree to having Russian forces permanently on Belarusian soil to maintain the weapons. Russia used Belarussian territory as a staging ground for sending its forces into Ukraine last year.

Although Belarus and Russia are generally in lockstep on everything, Mr. Lukashenko may yet weigh in with respect to who is responsible for what on his territory. 

While there is no denying that anything that involves the transfer of weapons with a nuclear component will exacerbate existing political faultiness in Europe, there are also indications from the Kremlin itself that this particular risk may be more moderate than some press reports indicate. President Putin likely saw the British admission as a clumsy chess move, but being Russian he had to find some chess piece to move up the board. 

In an interview on Russian television Saturday night, Mr. Putin said, “We are doing what they [the West] have been doing for decades, stationing [the weapons] in certain allied countries, preparing the launch platforms and training their crews,” Mr. Putin said, adding “we are going to do the same thing.” 

He also repeated the familiar refrain that Ukraine and its Western allies were to blame for the war, which in Russia is still referred to as a “military operation.” The West, he said,  “did it from the very beginning — in 2014, when they contributed to the coup d’état in Ukraine … you can reproach the former leadership for some mistakes, but this is an internal affair of Ukraine itself.” 

He added that “they are the instigators of this conflict,  and today, millions more ammunition, equipment, and so on are being handed over” to Ukraine, which “forced” the Kremlin to “protect” the population of Crimea, “one way or another.”

By pivoting to Crimea, the strategic peninsula Russia seized and annexed illegally in 2014, the Russian president essentially telegraphed where his heart and greed truly are, as he has done before. Many would make the argument that next to Crimea, the poster child for Mr. Putin’s neo-imperialist Russian ambitions, Belarus means next to nothing to him. 

The AP reported that Mr. Putin had initially objected to the depleted uranium rounds that Britain promised to ship to Ukraine by making the false claim that they have nuclear components. Yet there too he toned down his language even while insisting Saturday that the ammunition posed an additional danger to both troops and civilians in Ukraine by leaving a radioactive trace and contaminating agricultural land.

“Those weapons are harmful not just for combatants, but also for the people living in those territories and for the environment,” Mr. Putin said. 

That is possibly true, though it would be an almost comic consequence if owing to Ms. Goldie’s lack of inscrutability at London the Russian tyrant were to be mistaken for a man of compassion. 

Another sign that this latest crisis could be more of a wrinkle came from a former state secretary, Mike Pompeo. Speaking to Fox News’s Maria Bartiromo on Sunday, Mr. Pompeo said a real emerging danger stems from the growing military closeness of Russia and Communist China. In his estimation, it means that the nuclear arsenals of the two countries could eventually be considered as sitting under the same umbrella. 

No word yet from the Biden administration on that potential horror show.