Ukraine used US ATACMS missiles to strike Russian territory on Tuesday, taking advantage of newly granted permission from the outgoing Biden administration on the war’s 1,000th day.

Russia said its forces shot down five of six of the missiles, which were fired at a military facility in the Bryansk region. Debris of one hit the facility, starting a fire that was swiftly put out and caused no casualties or damage, it said.

Ukraine said it had struck a Russian arms depot around 110 km (70 miles) inside Russia in an attack that caused secondary explosions. The Ukrainian military did not publicly specify what weapons it had used, but a Ukrainian official source and a US official later confirmed it had used ATACMS.

President Joe Biden gave approval just this week for Ukraine to use the ATACMS, the longest-range missiles Washington has supplied, for such attacks inside Russia. Moscow has described their potential use as an escalation that would make Washington a direct combatant in the war and prompt its retaliation.

The attack took place as Ukraine marked 1,000 days of war, with weary troops at the front, Kyiv besieged by airstrikes, a fifth of Ukrainian territory in Moscow’s hands and doubts about the future of Western support as Donald Trump heads back to the White House.

Military experts say using the US missiles to attack positions at such a depth in Russia can help Ukraine defend a pocket of Russian territory it has captured as a bargaining chip, but is not likely to have a decisive impact on the course of the 33-month-old war.

Moscow has said such weapons cannot be used without direct operational support from the United States, and therefore their use would make Washington a direct participant in the war.

On Tuesday, President Vladimir Putin signed a new nuclear doctrine apparently intended as a warning to Washington. It lowers the threshold under which Russia might use atomic weapons to include responding to attacks that threaten its territorial integrity.

Washington said the update to the nuclear doctrine was no surprise and cited “more of the same irresponsible rhetoric from Russia”.

Jitters in markets

Reports of the Ukrainian attack caused jitters in markets, with share indexes sliding in Europe and safe haven assets rallying.

Trump has criticised the scale of US aid to Kyiv and said he will end the war quickly, without saying how. Both sides appear to anticipate his return in two months will be accompanied by a push for peace talks, which are not known to have taken place since the war’s early months.

The warring sides have both been escalating in recent weeks in an attempt to secure a stronger position at any negotiations. Ukrainian President Volodymyr Zelenskiy says Kyiv must do everything for the war to end diplomatically next year.

“At this stage of the war, it is being decided who will prevail. Whether us over the enemy, or the enemy over us Ukrainians… and Europeans. And everyone in the world who wants to live freely and not be subject to a dictator,” he said in an address to parliament on Tuesday marking 1,000 days of war.

A candle-lit commemoration was planned for later on Tuesday.

Thousands of Ukrainian citizens have died, over six million live as refugees abroad and the population has fallen by a quarter since Putin ordered the invasion by land, sea and air that began Europe’s biggest conflict since World War Two.

Military losses have been huge, although casualty figures remain closely guarded secrets. Public Western estimates based on intelligence reports say hundreds of thousands have been wounded or killed on each side.

“In the frozen trenches of the Donetsk region and in the burning steppes of the Kherson region, under shells, hail, and anti-aircraft guns, we are fighting for the right to live,” Ukraine’s top commander Oleksandr Syrkyi wrote on Telegram.

Tragedy has touched families in every corner of Ukraine, where military funerals are commonplace in cities and far-flung villages, and people are exhausted by sleepless nights of air raid sirens and anguish.

In the first year after the invasion, Ukrainian troops pushed Russian forces back from the outskirts of Kyiv and recaptured swathes of territory with surprise military successes against a larger and better-armed foe.

But since then, the enemies have settled into relentless trench warfare that has ground eastern Ukrainian cities to dust. Russian forces still occupy a fifth of Ukraine and for the past year they have steadily gained ground.

Kyiv now hopes to gain leverage from a sliver of territory in Russia’s Kursk region it captured after launching its first major cross-border assault in August. It says Russia has deployed 50,000 troops there to try to take it back.

In a move decried in the West as an escalation, Russia has now deployed 11,000 North Korean troops, some of whom Kyiv says have clashed with Ukrainian forces in Kursk. Zelenskiy said Pyongyang could send 100,000 soldiers.

Russia for its part continues to advance village by village in eastern Ukraine, claiming to have captured another settlement on Tuesday.

With winter setting in, Moscow on Sunday renewed its aerial assault on Ukraine’s struggling power system, firing 120 missiles and 90 drones in the biggest barrage since August.

Publicly there has been no narrowing of the gulf in the enemies’ negotiating positions. Kyiv has long demanded full Russian withdrawal from all occupied territory, and security guarantees from the West comparable to membership in NATO’s mutual defence treaty to prevent future Russian attacks.

The Kremlin says Ukraine must drop all ambitions to join NATO and withdraw all troops from provinces Russia claims to have annexed since its invasion.

Russia says Ukraine’s ATACMS strikes mark ‘new phase’ of war

Russia said on Tuesday that Ukraine’s use of long-range ATACMS missiles against its territory marked a “new phase of the Western war” against Moscow, and vowed to react “accordingly.”

“This is, of course, a signal that they want to escalate,” Russian Foreign Minister Sergei Lavrov, speaking at a G20 press conference in Brazil, said of the strike.

“We will be taking this as a qualitatively new phase of the Western war against Russia. And we will react accordingly,” he added, accusing Washington of helping Kyiv operate the missiles.

Russia has long asserted that the Army Tactical Missile System, known by its initials ATACMS, is programmed by US specialists and requires guidance from American satellites.

Lavrov also urged the West to read a decree signed by Russian President Vladimir Putin on Tuesday that lowers the threshold for when Moscow can use nuclear weapons.

“I hope that they will read this doctrine… in its entirety,” Lavrov said.