Russian President Vladimir Putin ordered a partial mobilization of reservists in Russia on Wednesday, risking a deeply unpopular step that follows a string of humiliating setbacks for his troops nearly seven months after invading Ukraine.

It’s the first call-up in Russia since World War II and is sure to further fuel tensions with the Western backers of Ukraine, who derided the move as an act of weakness. The move also sent Russians scrambling to buy plane tickets out of the country.

It comes after Russian authorities tried to recruit more fighters into volunteer battalions and amid reports of widespread recruitment in prisons, as the Kremlin has struggled to replenish its troops.

The Russian leader, in a seven-minute televised address to the nation aired Wednesday morning, also warned the West that he isn’t bluffing over using all the means at his disposal to protect Russia’s territory, in what appeared to be a veiled reference to Russia’s nuclear capability. Putin has previously warned the West not to back Russia against the wall and has rebuked NATO countries for supplying weapons to help Ukraine.

The total number of reservists to be called up could be as high as 300,000, officials said.

Even a partial mobilization is likely to increase dismay, or sow doubt, among Russians about the war in Ukraine. Shortly after Putin’s address, Russian media reported a sharp spike in demand for plane tickets abroad amid an apparent scramble to leave despite exorbitant prices for flights.

Kremlin spokesman Dmitry Peskov, who was asked what had changed since he and others previously said no mobilization was planned, argued that Russia is effectively fighting against NATO because the alliance’s members have been supplying weapons to Kyiv.

The partial mobilization order came a day after Russian-controlled regions in eastern and southern Ukraine announced plans to hold votes on becoming integral parts of Russia — a move that could set the stage for Moscow to escalate the war. The referendums will start Friday in the Luhansk, Kherson and partly Russian-controlled Zaporizhzhia and Donetsk regions.

The ballots are all but certain to go Moscow’s way. Foreign leaders have described the ballots as illegitimate and nonbinding. Ukrainian President Volodymyr Zelenskyy said they were a “sham” and “noise” to distract public attention.

Putin’s speech is “definitely a sign that he’s struggling, and we know that,” U.S. national security council spokesperson John Kirby said.

Putin has suffered tens of thousands of casualties, has command and control issues, terrible troop morale, desertion problems and is “forcing the wounded back (into) the fight,” Kirby said on ABC’s “Good Morning America.”

Only those with relevant combat and service experience will be mobilized, Russian Defense Minister Sergei Shoigu said. He added about 25 million people fit this criteria but only around 1% of them will be mobilized.

Another key clause in the decree prevents most professional soldiers from terminating their contracts and leaving service until the partial mobilization is no longer in place.

Putin’s announcement came as the U.N. General Assembly was taking place in New York. Moscow’s invasion of Ukraine on Feb. 24 has been the target of broad international criticism at the assembly that has kept up intense diplomatic pressure on Moscow.

Zelenskky is due to address the gathering in a prerecorded address on Wednesday. Putin didn’t travel to New York.

Putin’s gambit has a strong element of risk — it could backfire by making the Ukraine war unpopular at home and hurting his own standing. It also concedes that Russia has underlying military shortcomings.

A Ukraine counteroffensive launched this month has snatched the military initiative away from Russia, as well as capturing large areas in Ukraine that the Russians once held. The swiftness of the counteroffensive saw Russian forces abandon armored vehicles and other weapons as they beat hasty retreats.

A spokesman for Zelenskyy called the mobilization a “big tragedy” for the Russian people.

In a statement to The Associated Press, Sergii Nikiforov said conscripts sent to the front line in Ukraine would face a similar fate as ill-prepared Russian forces who were repelled in an attack on Kyiv in the first days of the war.

“This is a recognition of the incapacity of the Russian professional army, which has failed in all its tasks,” Nikiforov said.

The Russian mobilization is unlikely to produce any consequences on the battlefield for months because of a lack of training facilities and equipment.

The U.S. ambassador to Ukraine, Bridget Brink, tweeted that the mobilization is a sign “of weakness, of Russian failure.” British Defense Secretary Ben Wallace echoed that assessment, describing Putin’s move as “an admission that his invasion is failing.”

Russian political analyst Dmitry Oreshkin said Putin’s announcement smacked of “an act of desperation.” He predicted that Russians will resist the mobilization through “passive sabotage.”

“People will evade this mobilization in every possible way, bribe their way out of this mobilization, leave the country,” Oreshkin told The Associated Press on Wednesday.

The announcement won’t go down well with the general public, Oreshkin said, describing it as “a huge personal blow to Russian citizens, who until recently (took part in the hostilities) with pleasure, sitting on their couches, (watching) TV. And now the war has come into their home.”

The war in Ukraine, which has killed thousands of people, has driven up food prices worldwide and caused energy costs to soar. It has also brought fears of a potential nuclear catastrophe at Europe’s largest nuclear plant in Ukraine’s now Russia-occupied southeast. Investigations are also underway into possible war crimes atrocities committed by Russian forces in Ukraine.

In his address, which was far shorter than previous speeches about the Ukraine war, Putin accused the West of engaging in “nuclear blackmail” and noted “statements of some high-ranking representatives of the leading NATO states about the possibility of using nuclear weapons of mass destruction against Russia.”

He didn’t identify who had made such comments.

“To those who allow themselves such statements regarding Russia, I want to remind you that our country also has various means of destruction … and when the territorial integrity of our country is threatened, to protect Russia and our people, we will certainly use all the means at our disposal,” Putin said.

He added: “It’s not a bluff.”

Putin said he has already signed the decree for partial mobilization, which starts immediately, and stressed its limited scale.

“We are talking about partial mobilization, that is, only citizens who are currently in the reserve will be subject to conscription, and above all, those who served in the armed forces who have a certain military specialty and relevant experience,” Putin said.

Shoigu also said Wednesday that 5,937 Russian soldiers have died in the Ukraine conflict, far lower than Western estimates that Russia has lost tens of thousands.

The Vesna opposition movement called for nationwide protests on Wednesday.

“Thousands of Russian men — our fathers, brothers and husbands — will be thrown into the meat grinder of the war. What will they be dying for? What will mothers and children be crying for?” the group said.

Yet it was unclear how many would protest given Russia’s harsh laws against criticizing the military.