President Vladimir V. Putin of Russia replaced his minister of defense on Sunday with an economist, shaking up his national security team for the first time since his invasion of Ukraine and signaling his determination to put Russia’s war effort on an economically sustainable footing.

Mr. Putin kept the minister, Sergei K. Shoigu, in his inner circle, tapping him to run the country’s security council — a position giving Mr. Shoigu close access to the president but little direct authority. Mr. Shoigu will replace Nikolai P. Patrushev, a former K.G.B. colleague of Mr. Putin, who the Kremlin said would be moved to another position to be announced in the coming days.

Andrei R. Belousov, an economist who had served as first deputy prime minister since 2020 and long been seen as one of Mr. Putin’s most trusted economic advisers, was nominated to become the new defense chief.

The Kremlin said Russia’s ballooning defense budget warranted putting an economist in charge, and that Mr. Belousov would help make the Russian military “more open to innovation.”

The cabinet shifts represented a rare overhaul for Mr. Putin, who tends to avoid rash changes, and they could mark a turning point in Russia’s more than two-year war in Ukraine.

He removed from the military’s helm a man whom Russian pro-war commentators and Western analysts alike held partly responsible for Moscow’s many failures at the outset of the invasion. And by installing an economist, he tacitly acknowledged the importance of industrial might to any military victory.

Mr. Shoigu’s potential dismissal was an object of speculation from the war’s first days, when Russian forces appeared unprepared for the determination of Ukraine’s resistance.

Last summer, the mercenary chief Yevgeny V. Prigozhin staged a mutiny to try to remove Mr. Shoigu, the defense minister for more than a decade. But Mr. Putin, who analysts say values loyalty, stuck with Mr. Shoigu.

Now, with the Russian military having gained the battlefield initiative, Mr. Putin is signaling a greater willingness to make changes and to show that Russia has the discipline and economic capacity to wage a long war. A possible shift in Mr. Shoigu’s stature was telegraphed last month, when the Russian authorities arrested one of his top deputies on corruption charges.

But the Kremlin said on Sunday that another frequent target of critics of Russia’s war effort — Gen. Valery V. Gerasimov, the chief of the Russian general staff and the highest-ranking Russian military officer — would remain in his post.

It is unclear how much authority over the war Mr. Shoigu will retain. While his new job parallels that of the American president’s national security adviser, analysts say that in Mr. Putin’s Russia, the role has limited influence because it does not directly control the military or a security agency.

Mr. Shoigu was “too big to fall,” Alexander Baunov, a senior fellow at the Carnegie Russia Eurasia Center, wrote. But in his new role, he added, Mr. Shoigu would be “without real command powers and without a cash box.”

Mr. Belousov, 65, who was a Kremlin economic adviser before being named first deputy prime minister in 2020, comes from the so-called economic bloc of the government, which won plaudits within the Kremlin for its agile response to Western sanctions and success in stabilizing the country’s economy.

The security bloc of the government, by contrast, was subject to recriminations after the Russian military pursued a faulty strategy in the early months of the war and faltered on the battlefield.

Russian commentators expressed surprise over the appointment of an economist to oversee Russia’s sprawling military. The Kremlin’s spokesman, Dmitri S. Peskov, told reporters that Mr. Putin made the decision as Russia was once again approaching Soviet-era levels of military expenditure due to “geopolitical circumstances.”

“This is extremely important and it requires special attention,” Mr. Peskov said.

He added that Mr. Putin wanted his defense ministry to be under civilian leadership because of the need to modernize the military — an implicit message that Mr. Shoigu was not up to the task. (Mr. Shoigu held a rank of general because of his previous role as emergencies minister.)

“Today on the battlefield, the victor is the one who is more open to innovation, more open to the most rapid implementation,” Mr. Peskov said. “So it’s natural that at the current stage the president decided that the defense ministry be headed by a civilian.”

Still, despite his knowledge of economics, Mr. Belousov has relatively little executive experience. He served as the country’s minister of economic development for a little over a year, from 2012 to 2013.

The change comes less than a week after Mr. Putin was inaugurated to his fifth term as Russia’s president, a ritual that was widely expected to set the stage for a cabinet shuffle of some kind. The Russian leader’s entire cabinet was dissolved as part of the government transition. Many but not all of his ministers were renominated to their posts.

Mr. Shoigu was the longest-serving minister in the history of the independent Russian Federation and a fixture of Russian politics since the collapse of the Soviet Union.

Originally from the Tuva Republic in southern Siberia, he developed a national profile as a man of action by serving as Russia’s emergencies minister for more than two decades, from 1991 to 2012. He could regularly be found on television responding to the country’s natural disasters, in contrast to other ministers portrayed as paper pushers.

Mr. Shoigu’s tenure as Russia’s defense minister, beginning in 2012, was marked by Mr. Putin’s military intervention in Ukraine in 2014 and in Syria in 2015. Then in 2022, Mr. Shoigu became a lightning rod for criticism as the Russian military faltered in the early months of the war.

For months last year, Mr. Prigozhin railed against him in videos posted online, assailing him for incompetence in a fight for influence that ultimately ended with the mercenary leader trying to oust him in a failed uprising last summer. Mr. Prigozhin later died in a plane crash that U.S. officials believed was likely to have been a Kremlin-approved assassination.

The leadership changes Sunday also may signal a change in stature for Mr. Patrushev, a hard-liner with a K.G.B. background who has long been seen as a member of Mr. Putin’s inner circle.

It is unclear what new position he will be offered.

With war costs rising, Mr. Putin’s government has embarked on an effort to raise more revenue, including with a planned overhaul of the country’s tax system.

Nearly a third of the Russian federal budget has been allocated to national defense this year, a huge increase from previous years. The intense government spending on the military has turbocharged the Russian economy but raised the risk of overheating, as a crimped labor force drives up wages and inflation.

One of Mr. Shoigu’s top deputies, Timur Ivanov, was arrested by Russian authorities in April and accused of bribery. Mr. Ivanov had long been in charge of military construction projects.

His arrest, the removal of Mr. Shoigu and the installation of a trusted technocrat to head the defense ministry may also be a signal that the Kremlin, after turning a blind eye to corruption that has blossomed alongside military spending, will now mount a campaign to rein in graft in the sector.

“Belousov’s first task will be fighting corruption,” Sergei Markov, a pro-Kremlin political analyst, wrote on the Telegram messaging app, referring to the newly appointed defense minister. For Mr. Belousov, he added, “the post of defense minister during a hybrid war against the entire West is the most important challenge of his life.”