Mikhail Kasyanov told Newsweek that protests across the country would gather pace in the coming months because Putin’s decree will alienate him from those who had backed him until now.

Since the start of Putin’s full-scale invasion on February 24, the Kremlin had repeatedly assured the Russian population that its forces would only need professional troops to prevail. But now the conflict viewed on state television at home has taken on a new dynamic.

More than 1,300 people were reportedly arrested in 38 cities across the country on Thursday for opposing Putin’s decree to call up 300,000 reservists to prop up his faltering military campaign.

“His decision means that even those people who were neutral or supported Putin, in general, will start reconsidering their attitude because of the fact that they are now obliged to go to a war they were previously watching,” Kasyanov told Newsweek.

“The war no longer affects those in the professional army from poor families,” he said, but now it “touches everyone.”

By December, Kasyanov predicted that Putin will face the pressure of dissent dovetailing with the full impact of western sanctions and further Ukrainian gains.

The Moscow prosecutor’s office has warned that those who take part in demonstrations could face long jail terms. There is a clampdown on those who dispute the Kremlin narrative about the war in Ukraine.

But according to Kasyanov, many would prefer that to serving in Ukraine.

“Those people don’t want to go to war to kill Ukrainians and be killed,” he said.

While he does not expect those in Putin’s inner circle to revolt immediately, Kasyanov said that “they will not implement his instructions in an absolute manner.”

His instructions “will not be implemented by his agencies,” he said. “It is already clear people are tired of his leadership.”

Kasyanov believed this would lead to a “gradual dilution of his strength and power.”

“It will start gradually, minimizing his authority,” he said. While regarding his ouster, “I cannot say how long it will take.”

Kasyanov, 64, was Russia’s prime minister from 2000 to 2004, during Putin’s first term. It was an era of transformation towards growth following a domestic default in 1998 under President Boris Yeltsin that lowered its standing in the world.

“Putin supported all the reforms my cabinet initiated,” Kasyanov said. “At that time, we brought Russia to economic growth. After my departure, he changed completely.”

Now a leading critic of Putin, Kasyanov was a candidate in Russia’s 2008 presidential election but in the middle of the campaign was denied the ability to participate on political grounds.

In 2010, he co-founded the coalition People’s Freedom Party “For Russia without Lawlessness and Corruption” and was a prominent participant in the Russian protests for fair elections between 2011 and 2013. He has been the leader of the People’s Freedom Party (PARNAS) since 2015.

Putin’s decree was a “last resort,” said Kasyanov, who is no longer in Russia. “It is a recognition of his failure.”

Newsweek reached out to the Kremlin for comment.

Update 9/22/22 9:43 a.m. ET: This story has been updated with a new photo.