President Vladimir Putin visited Russia’s Kursk region for the first time since Moscow claimed that it drove Ukrainian forces out of the area, the Kremlin said Wednesday.

The Russian military had announced its troops have fully reclaimed the border territory in late April — nearly nine months after losing chunks of the region on the border with Ukraine to a surprise Ukrainian incursion.

Ukraine has denied the claim and has indicated that its troops were still present in the Kursk region. Losing control of the land in Kursk would deprive Kyiv of key leverage in any negotiations to end the 3-year-old war by exchanging its gains for some of Russian-occupied land in Ukraine.

Here are key moments of the battle for Kursk and its impact:

A Ukrainian blitz

Ukrainian forces pushed into Kursk on Aug. 6, 2024, in a stunning attack, with battle-hardened mechanized units quickly overwhelming lightly armed Russian border guards and inexperienced army conscripts. Hundreds were taken prisoner.

The incursion was a humiliating blow to the Kremlin — the first time the country’s territory was occupied by an invader since World War II.

It was plotted in complete secrecy, with the Ukrainian troops involved reportedly told of their mission only a day before it began. Russia’s drones and intelligence assets were focused on battlefields in eastern Ukraine, which enabled Kyiv to pull its troops covertly to the border under the cover of thick forests.

Ukrainian units quickly drove deep into the Kursk region in several directions, meeting little resistance and sowing chaos and panic. As the most capable Russian units were fighting in the Donetsk region of eastern Ukraine, Moscow didn’t have enough land forces to protect the Kursk region and other border areas.

Putin visits Russia’s Kursk for first time since Moscow claims to oust Ukrainian forces

Ukrainian President Volodymyr Zelenskyy cast the incursion as a way to distract Russian forces in the east and said Kyiv could eventually exchange its gains for Russian-occupied territory in peace talks.

Ukraine’s chief military commander, Gen. Oleksandr Syrskyi, said Kyiv’s forces captured nearly 1,300 square kilometers (500 square miles) and about 100 settlements in the region that covers 29,900 square kilometers (11,540 square miles). Unlike the static front lines in Donetsk, Ukrainian units were able to roam the region without establishing a lasting presence in many settlements they seized.

While the incursion came as a much-sought morale boost for Ukraine amid battlefield setbacks, skeptics saw it as a dangerous gamble that distracted some of its most capable forces from Donetsk, where Kyiv was steadily losing ground to the Russian offensive.

Russia’s slow response

In the incursion's opening days, Russia relied on warplanes and helicopters because it lacked ground forces to stop the onslaught.

At the same time, Moscow began pulling a motley collection of reinforcements from all over Russia, some of whom lacked combat experience and had trouble coordinating with each other, contributing to Ukraine’s swift gains.

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But contrary to Kyiv's hopes, the incursion didn’t force Moscow to shift a significant number of troops there. Since Russia lacked the resources to expel the attackers quickly, it focused on stemming deeper Ukrainian advances by sealing roads and targeting Kyiv’s reserves.

North Korea's role

In the fall, Ukraine, the United States, and South Korea said North Korea — which previously had supplied weapons to Moscow — had also deployed 10,000-12,000 troops to Russia to fight in Kursk.

Moscow and Pyongyang initially responded vaguely to the reports of the North Korean deployment, emphasizing that their military cooperation conforms with international law, without directly admitting the troops' presence. However, last month they confirmed the deployment.

Reporting to Putin on reclaiming seized areas in Kursk on April 26, Russia’s General Staff chief Gen. Valery Gerasimov said North Korean soldiers took part in “combat missions shoulder to shoulder with Russian servicemen during the repelling of the Ukrainian incursion.”

In a statement on the Kremlin's website two days later, Putin praised North Korean soldiers, saying the “Russian people will never forget" their heroism.

"We will always honor the heroes who gave their lives for Russia, for our common freedom, fighting side by side with their Russian brothers in arms,” Putin said.

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While North Korean soldiers are highly disciplined and well-trained, Ukraine and its allies said they suffered heavy casualties from drone and artillery attacks due to a lack of combat experience and unfamiliar terrain.

In January, South Korea’s National Intelligence Service said about 300 North Korean soldiers had died and another 2,700 had been injured. Zelenskyy had earlier put the number of killed and wounded North Koreans at 4,000, although U.S. estimates were lower, about 1,200.

South Korea's spy agency said in February that North Korea apparently had sent additional troops to Russia.

Russia intensifies efforts to reclaim Kursk

The Kremlin bolstered Russian forces in Kursk in the fall, and they gradually intensified their effort to drive out the Ukrainians.

By February, Russia reclaimed about two-thirds of the captured territory, leaving Ukraine with an area around Sudzha, a border town that was Ukraine's main hub in the region.

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Pressure on Ukrainian troops sharply increased in March, when Russian forces sought to cut a corridor between Sudzha and Ukraine’s Sumy region across the border. Russian artillery and drones relentlessly pummeled the road, which was littered with the carcasses of military hardware that made it hard for Ukraine to ferry supplies and rotate troops.

The interdiction of supply routes put Ukrainian forces in a difficult position, said Michael Kofman of the Carnegie Endowment. “As the Kursk pocket got squeezed, it became increasingly unsustainable,” he said.

In a daring raid in early March, 600 Russian troops crawled 15 kilometers (over 9 miles) through a natural gas pipeline and emerged near Sudzha to strike Ukrainian troops from the rear.

The operation came as the U.S. halted weapon supplies and intelligence-sharing with Ukraine, a move that followed an acrimonious White House meeting on Feb. 28 between Zelenskyy and President Donald Trump. After talks with Ukraine on March 11, when Kyiv agreed to accept a 30-day ceasefire proposal, the U.S. said it was unfreezing the assistance.

Consequences for Ukraine

Ukraine's military General Staff in April dismissed Moscow's claim of retaking full control of Kursk and published a map Wednesday suggesting Ukrainian troops still were present in small parts of the region near the border.

Losing control over land in Kursk would weaken Kyiv’s hand in any peace talks, removing its bargaining chip for exchanging territory it lost earlier in the war.

Russia holds about a fifth of Ukraine, and Kyiv’s defeat in Kursk would also raise the threat of Moscow's farther advance in the Sumy border region.

On a visit to Russian military headquarters in Kursk last month, Putin set the task of carving a “security zone” along the border, a signal his military was considering a possible foray into Sumy.

Gerasimov said in late April that the efforts to create a security zone in Sumy's border areas were ongoing, and that the Russian military controlled over 90 square kilometers (35 square miles) there.