Three weeks ago, Ukraine’s military launched a stunning operation to take the war in Ukraine back onto the territory of the country that launched it. Three weeks later, the Ukrainians still occupy hundreds of miles of territory in Russia’s western Kursk region.

The incursion had a number of goals: to force Russia to divert its forces from Ukraine to defend its own towns and cities; to seize territory that might later be used for bargaining leverage in peace negotiations; and to send a political message to the Russian people and their leaders that they are not safe from the consequences of the war launched by Russian President Vladimir Putin nearly two-and-a-half years ago.

But there was also a less obvious objective: Leaders in Kyiv likely hoped to send a message to their friends in the United States and Europe that their approach to the war has been overly cautious — that fears about “escalation,” “red lines,” and Russian nuclear use — a threat that Putin himself has voiced repeatedly — have been overblown.

Ukrainian President Volodymyr Zelenskyy acknowledged this explicitly in a speech on August 19, saying, “We are now witnessing a significant ideological shift, namely, the whole naive, illusory concept of so-called ‘red lines’ refs somewhere near Sudzha” — a town near the border now under the control of Ukrainian forces.

He also confirmed that Ukraine had not informed its Western partners about the operation ahead of time, anticipating that they would be told “it was impossible and that it would cross the strictest of all the red lines that Russia has.” According to press reports, the Ukrainians predicted — correctly, as it turned out — that the West would not object too strongly once presented with a fait accompli.

“They were trying to push a boundary with their Western partners and what we’ve seen is that these partners have quietly accepted the new boundary,” said Liana Fix, fellow for Europe and the Council on Foreign Relations. In particular, they’re hoping the US will lift restrictions on using American-provided long-range missiles to strike deep into Russia, a step Washington has so far avoided.

In apparent retaliation for the Kursk invasion, Moscow on Monday launched the largest missile and drone barrage on Ukraine since the start of the war. But that still fell far short of the nuclear escalation that Putin has often threatened.

In his speech, Zelenskyy was arguing, in effect, that he had called Putin’s bluff and that it’s time for Ukraine’s allies to become much more aggressive in giving Ukraine the kind of support it needs to win the war.

Since Russia’s full-scale invasion in 2022, Ukraine’s Western backers, including the United States, have had two priorities: preventing Russian victory and avoiding “escalation” — meaning avoiding direct combat between Russia and NATO militaries or, in a worst-case scenario, use of nuclear weapons. At times, the second priority has taken precedence over the first.

The Russian government has certainly done everything in its power to add nuclear uncertainty to Western leaders’ calculations. From the very first day of the invasion, Putin has made repeated references to his country’s nuclear arsenal — the largest in the world — and warned countries that get in Russia’s way of “consequences that you have never faced in your history.”

Over the course of the war, Putin and other Russian officials have made repeated references to “red lines” that should not be crossed if Western governments don’t want to face a catastrophic response. Former Russian President Dmitry Medvedev has been particularly active in threatening foreign powers with “nuclear apocalypse” via his social media accounts.

It’s not all rhetoric: The Russian government has taken steps such as moving some of its nuclear weapons to Belarus and conducting realistic drills for using tactical nuclear weapons — seemingly in an effort to remind Ukraine’s allies of Russia’s capabilities.

“Beyond North Korea, the Russians have been the country that has used nuclear threats most vigorously,” said Nicole Grajewski, a fellow in the Nuclear Policy Program at the Carnegie Endowment for International Peace.

The threats work — but only to a certain extent and only for a time. Escalation fears were the reason Western countries ruled out taking actions like imposing a no-fly zone in Ukraine or sending NATO troops into the country.

Escalation fears have also made them reluctant to provide certain weapons systems to Ukraine, though system-by-system, that reluctance has faded over time. There was a time when even shoulder-mounted stinger missiles were viewed as too provocative. Now, the Ukrainians are using US-provided long-range missiles and recently received their first batch of F-16 fighter jets.

That these capabilities have often been provided only after months of contentious political debate has been an endless source of frustration to Ukrainians.

“I’ve been hearing about nuclear escalation since the first day,” Oleksandra Ustinova, a Ukrainian member of parliament who chairs a committee monitoring arms supplies, told Vox last June. “First it was, it was ‘if Ukraine gets MIGs from Poland, he’s going to use nukes.’ Then it was the HIMARS, then Patriots, then tanks.”

She added: “It’s like we’re running behind the train. Every time we ask for something, we get it months or a year later when it won’t make as much of a difference as it would have before.”

The fact that none of the steps Western countries have taken so far have resulted in Russia using a nuclear weapon or directly attacking a NATO country is taken by many Ukrainians and their international supporters as evidence that these threats were never real to begin with.

If anything could be considered crossing a “red line,” one would think it would be the first military invasion of Russian territory since World War II.

Russia’s official nuclear doctrine permits the use of nuclear weapons under circumstances in which the “very existence of the state is in jeopardy.” Ukraine’s incursion into the Kursk region, which has seized hundreds of square miles of territory, might not be a direct threat to the regime in Moscow, but it certainly threatens that regime’s ability to defend its own territory and sovereignty — the basic function of any state.

Moreover, the Ukrainians appear to be using US-provided weapons inside Russian territory, in apparent violation of US policy. (The Biden administration agreed in May to allow the Ukrainians to use American weapons for limited strikes into Russia, but only to defend against attacks on Ukraine.)

And yet, there’s been markedly little saber-rattling from Putin and the Kremlin since the Kursk operation began. The president has downplayed what he calls a “large-scale provocation” and has taken a few seemingly unrelated trips in what appears to be an effort to project normalcy.

The picture in the Russian media has been a bit more mixed: Vladimir Solovyov, host of the flagship pro-Kremlin talk show Sunday Evening, used one monologue to both call on Russians to “calm down a bit” about the incursion and to call for nuclear strikes on European capitals.

Regardless of what Solovyov says, it does not appear that Russia is planning to respond to the events in Kursk by using nuclear weapons, attacking NATO countries, or taking steps beyond — as we saw with Monday’s massive barrage — destroying more of Ukraine with conventional weapons.

This doesn’t, however, mean that Ukraine’s backers are ready to take the gloves off.

During a press call on Friday, Vox asked US National Security Spokesperson John Kirby whether Zelenskyy was right that it was time to move beyond fears of escalation.

“We’ve been watching escalation risks since the beginning of this conflict, and that ain’t gonna change,” Kirby responded. “We’re always going to be concerned about the potential for the aggression in Ukraine to lead to escalation on the European continent.” He added that “it’s too soon to know whether what’s going on in Kursk…[what] potential impact that that could have in terms of escalation. But it is something that we remain concerned about.”

The thinking in the administration appears to be that, as Pentagon Deputy Spokesperson Sabrina Singh recently put it, “just because Russia hasn’t responded to something doesn’t mean that they can’t or won’t in the future.” And given that it’s nuclear weapons we’re talking about, that’s a risk that has to be taken seriously.

“Even if it’s only a 10 percent chance or 5 percent chance that they actually mean it, or they’re actually planning to act on it, that’s concerning enough,” said Carnegie’s Grajewski.

Pavel Podvig, senior researcher on Russia’s nuclear arsenal at the United Nations Institute for Disarmament Research in Geneva, argues that “this whole kind of a business of red lines is actually quite misleading and not helpful.”

In his view, there are few useful military applications for nuclear weapons inside Ukraine and given the catastrophic risks involved, Putin would be unlikely to consider any sort of nuclear use unless the very existence of the Russian state were threatened. “Even the loss of a region like Kursk technically would not qualify,” Podvig said.

Putin has certainly implied, however, that his threshold for escalation was much lower. Just last May, for instance, he warned Western countries against allowing their weapons to be used to strike Russian territory, saying they should “bear in mind our parity in the field of strategic weapons.” (“Strategic” is a euphemism for nuclear in this case.) These threats are getting harder to take seriously.

Kyiv’s current campaign is to get the US to lift its restrictions on using US-supplied long-range missiles to strike deep into Russia, which would allow them to press the offensive in Kursk further and hit more Russian military targets than they are currently able to with domestically produced weapons.

“Ukraine is separated from halting the advance of the Russian army on the front by only one decision we await from our partners: the decision on long-range capabilities,” Zelenskyy said in his speech. In a post on Twitter following Monday’s strikes, Ukraine’s defense minister said the attack showed why “Ukraine needs long-range capabilities and the lifting of restrictions on strikes on the enemy’s military facilities.”

If this debate follows the trajectory of those that preceded it, Washington will eventually come around to giving the Ukrainians what they’re asking for. But while the risky incursion into Kursk may have given Ukraine some more ammunition in these debates going forward, Western leaders are not about to simply abandon their caution and give Ukraine everything it wants.

As the Council on Foreign Relations’s Fix put it, Western “red lines” on aid to Ukraine have clearly shifted. The problem is “we don’t know how the red lines are shifting in Putin’s mind.”