Artem Shmyrev had everyone fooled. The Russian intelligence officer seemed to have built the perfect cover identity. He ran a successful 3-D printing business and shared an upscale apartment in Rio de Janeiro with his Brazilian girlfriend and a fluffy orange-and-white Maine coon cat.

But most important, he had an authentic birth certificate and passport that cemented his alias as Gerhard Daniel Campos Wittich, a 34-year-old Brazilian citizen.

After six years lying low, he was impatient to begin real spy work.

“No one wants to feel loser,” he wrote in a 2021 text message to his Russian wife, who was also an intelligence officer, using imperfect English. “That is why I continue working and hoping.”

He was not alone. For years, a New York Times investigation found, Russia used Brazil as a launchpad for its most elite intelligence officers, known as illegals. In an audacious and far-reaching operation, the spies shed their Russian pasts. They started businesses, made friends and had love affairs — events that, over many years, became the building blocks of entirely new identities.

Major Russian spy operations have been uncovered in the past, including in the United States in 2010. This was different. The goal was not to spy on Brazil, but to become Brazilian. Once cloaked in credible back stories, they would set off for the United States, Europe or the Middle East and begin working in earnest.

The Russians essentially turned Brazil into an assembly line for deep-cover operatives like Mr. Shmyrev.

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President Vladimir V. Putin of Russia visited the Kursk region in the west of the country for the first time since Moscow’s troops drove Ukrainian forces out of most of the territory they had seized there in a surprise cross-border offensive.

The Kremlin said on Wednesday that Mr. Putin went to Kursk’s nuclear power plant a day earlier, led a meeting with local government officials and met with volunteers helping residents affected by the conflict. Images and videos of the trip released by the Kremlin were seemingly aimed at projecting a return to normality, even as fighting still raged in one corner of the region.

The visit came days after Russian and Ukrainian officials met for the first direct peace talks in more than three years.

Mr. Putin had previously indicated that he would not negotiate with Ukraine until its forces surrendered in Kursk, while Kyiv had hoped to use its control over Russian land as leverage in any talks to end the war. The visit could signal that Mr. Putin, the Russian leader, believes one barrier to negotiations has been removed, even as Ukraine continues to mount small-scale attacks on the Russian side of the border.

Ukrainian forces launched an incursion into Kursk in August and quickly seized some 500 square miles of Russian territory. But the push slowed after a few weeks and Ukrainian troops began to lose ground as Russian forces deployed there in greater numbers. With the help of North Korean soldiers, Russian forces managed to chip away at Ukrainian-occupied territory before launching a decisive counterattack in March that reclaimed most of Kursk.

The Ukrainian military still holds a sliver of Russian territory along Kursk’s border, according to DeepState, a group of analysts who map the battlefield. It has continued probing Russian defenses in other border areas, too.

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