A trifecta of new developments in the Russo-Ukrainian war is a reminder of how what to some seems like only a regional skirmish could spill over into something more explosive — starting with a stark Russian warning about nuclear escalation. Russia’s deputy foreign minister, Sergei Ryabkov, said as much on Wednesday with words to the effect that the risk of nuclear conflict was at its highest level in decades.

That was actually a repeat warning, paired with a declaration that Moscow is in a “de facto” open conflict with Washington over the situation in Ukraine.

In February Russia suspended its participation in the New Start nuclear arms reduction treaty. Almost too fittingly, Mr. Ryabkov spoke at an event entitled “A World Without START: What Happens Next.” According to Interfax, he said, “I wouldn’t want to dive into a discussion about whether the likelihood of a nuclear conflict is high today, but it is higher than anything we have had for the past few decades, let’s put it that way.” 

Put another way, Russia has embarked on a perilous path, its pouting over Start going hand in hand with what Mr. Ryabkov referred to as Washington’s “hostile course” toward Moscow and a refusal to put Russia’s Start plug back in the socket. 

Similar language has emanated in recent days from President Putin and his defense minister, Sergei Shoigu. Their attention, though, has momentarily at least been diverted by Britain’s plans to send tank munitions containing non-enriched uranium  — otherwise known as depleted uranium, or DU — to Ukraine. On Tuesday Mr. Putin said the United Kingdom “announced not only the delivery of tanks to Ukraine but also shells containing non-enriched uranium … if this happens, Russia will be forced to respond.”

The Russian strongman’s comments were a reaction to a statement on Monday by a junior British defense minister in the House of Lords, Annabel Goldie. She said that “armor piercing rounds which contain depleted uranium” would be given to Ukraine along with the 14 Challenger 2 tanks from Britain. It is worth noting that Moscow has in its own stockpile of Svinets-2 depleted uranium tank shells.

Yet the controversy over the depleted uranium rounds is only heating up. A headline in Milan’s Corriere della Sera sums up some European sentiment, “Depleted uranium, from Bosnia to Iraq: the dirty, low-cost weapon not yet banned.” The Italian daily reported that many organizations including the UN have tried to ban the substance but to no avail, due largely to British and French resistance. DU contamination has been linked to birth defects and tumors and has been an issue in Iraq.

Another leading Italian newspaper, La Stampa, also took issue with the British stance on depleted uranium rounds. That paper’s chief foreign affairs analyst, Dominic Quirico, says that “with uranium bullets London risks dragging the Ukraine conflict towards a nuclear horizon.”

That is probably an overstatement, but throwing DU into the equation just exacerbates the overall plight of “poor Ukraine,” as the Milanese newspaper puts it, and underscores a deepening European frustration with what feels on the Continent like a war with no end in sight and no strategy from the White House other than unstinting support for Kyiv for “as long as it takes” — which few could argue constitutes an actual strategy. 

If growing foreign involvement in the war decoupled from any meaningful diplomatic pressure is meant to deter the Kremlin, it is not clear if that is really the case. Civilian targets are still coming under attack from missile and drone strikes. On Wednesday a Russian missile struck a nine-story apartment building in the southeastern city of Zaporizhzhia, killing at least one person. Moscow’s forces also launched exploding drones shortly before dawn, the AP reported, killing at least eight people in or around a student dormitory near Kyiv.

Also on Wednesday, a Republican senator of South Carolina, Lindsey Graham, told Secretary Blinken at a Senate hearing, “We made a mistake by not having pre-invasion sanctions” of Russia. He added, “We should have supplied more weapons to Ukraine before the invasion, to deter the war. China is now openly embracing Russia. We are at a tipping point here.”

Mr. Blinken had little of substance to say in response, and resisted Mr. Graham’s recommendation to label Russia a state sponsor of terror. The senator was hardly exaggerating. Beyond the increasingly messy war of attrition along Ukraine’s eastern frontlines and despite Beijing’s pernicious influence, Ukraine is dialing up its counter strikes in Russian-occupied Crimea, which Mr. Blinken has previously called a red line for Mr. Putin. 

Be that as it may, Ukraine is flexing its muscle on, and over, the strategic peninsula. On Monday reports emerged of a Ukrainian strike on a convoy of Kalibr cruise missiles at Dzhankoi in northern Crimea. The missiles that were destroyed were meant to be positioned on Russian ships and submarines. Ukrainian officials said the strike would help to “demilitarize Russia and prepare the Crimean peninsula for de-occupation.”

Then on Wednesday Russia claimed to have shot down “three objects,” likely Ukrainian naval drones, over the heavily fortified Crimean port of Sevastopol. Russia is girding for more: There are widespread reports of increased patrols, installation of mobile physical barriers at the entrance to the airport, moving ships inland, and reinforcing anti-aircraft batteries.

Credit the Ukrainians for being proactive. Significant American support notwithstanding, President Biden’s approach to the festering conflict is still largely reactive. That only kicks solutions down the road, clears the way for Chinese and Iranian meddling, and keeps Vladimir Putin and Volodymr Zelensky at each other’s throats. What should raise some alarms is that while each is younger than Mr. Biden, neither seems as tired.