The Ukrainian army's swift incursion into the Russian border region of Kursk is the largest such cross-border attack by Kiev forces in the nearly two-and-a-half-year open war, which exposed Russia's vulnerability and dealt a painful blow to the Kremlin.
The surprise attack has forced thousands of civilians to flee the region as the Russian military struggles to repel the Ukrainians.
For Ukraine, the cross-border attack offers a much-needed boost to public morale at a time when its undermanned and underarmed forces have faced relentless Russian attacks along a front line more than 1.000 kilometers long.
Kiev troops entered the Kursk region early Tuesday from several directions, quickly overrunning several checkpoints and field fortifications with lightly armed border guards and infantry units along the region's 245-kilometer border with Ukraine.
Unlike earlier incursions carried out by small groups of Russian volunteers fighting alongside Ukrainian forces, the incursion into the Kursk region reportedly involved combat-hardened units of several brigades of the Ukrainian army.
Russian military bloggers reported that Ukrainian mobile groups consisting of several armored vehicles quickly drove dozens of kilometers into Russian territory, bypassing Russian fortifications and spreading panic throughout the region.
The Institute for the Study of War, a Washington-based think tank, said Ukrainian forces had managed to penetrate up to 35 kilometers deep into the region.
"Ukrainian forces appear to be able to use small armored groups to carry out attacks due to the low density of Russian personnel in the border areas," the analysis said.
In doing so, Ukrainian forces have massively used drones to attack Russian military vehicles and deployed electronic warfare assets to suppress Russian drones and disrupt military communications.
While small Ukrainian mobile groups roamed the region without trying to consolidate control, other troops reportedly began digging in around the town of Suja, 10 kilometers from the border, and in some other areas.
Caught off guard, the Russian troops failed to respond quickly to the incursion. With most of the Russian military engaged in an offensive in Ukraine's eastern Donetsk region, few troops are left to protect the border region of Kursk. The Russian units along the border consisted mainly of poorly trained conscripts who were easily overpowered by the elite Ukrainian units. Some conscripts were captured.
The manpower shortage prompted the Russian military command to initially rely on fighter jets and helicopters to try to stop the Ukrainian offensive. At least one Russian helicopter was shot down and another was damaged by Ukrainian forces as they advanced, according to Russian military bloggers.
Russian reinforcements, including elite special forces units and hardened "Wagner" veterans, later began arriving in the Kursk region, but have so far failed to dislodge Ukrainian forces from Suja and other areas near the border.
Some of the newly arrived troops lacked combat skills and suffered losses. In one instance, a convoy of military trucks carelessly stopped en route near a combat zone and was hit by Ukrainian fire.
The Russian Ministry of Defense announced on Friday that Ukraine had lost 945 soldiers in four days of fighting. That claim could not be independently verified. The ministry did not offer any data on Russian casualties.
Ukrainian officials refrained from commenting on the cross-border attack. In a video address to the nation on Thursday, Ukrainian President Volodymyr Zelensky avoided directly mentioning the fighting in the Kursk region. But he said that "Russia has brought war on our country and it should feel what it has done."
Zelenskiy's adviser, Mihajlo Podoljak, said on Thursday that the cross-border attacks would make Russia "begin to realize that the war is slowly creeping into Russian territory." He also suggested that such an operation would improve Kiev's position in future negotiations with Moscow.
"When will it be possible to conduct the negotiation process in such a way as to pressure the Russians or to get something from them? Only when the war does not take place according to their scenario," he said.
Russian President Vladimir Putin described the incursion as a "large-scale provocation" with "indiscriminate shelling of civilian buildings, residential houses and ambulances".
Russian authorities said at least five civilians, including two emergency personnel, were killed and nearly 70 wounded in a Ukrainian attack on the Kursk region.
Dmitry Medvedev, deputy head of the Security Council chaired by Putin, said the Ukrainian action underscored the need for Moscow to expand the war and seize more of Ukraine's territory, including the capital Kiev, the Black Sea port of Odessa and other major cities.
Russia has declared a general state of emergency in the Kursk region, giving local authorities more powers to quickly coordinate emergency response. Russian state propaganda has focused on the Kremlin's efforts to provide aid to displaced residents, while downplaying the military's unwillingness to attack.
By launching the incursion, Kiev could aim to force the Kremlin to divert resources from the eastern Donetsk region, where Russian forces have launched offensives in several sectors and achieved slow but steady success, relying on their firepower advantage.
At a time when KI forces are struggling to stop Russia's advance in the east, the swift cross-border attack shows Ukraine's ability to take the initiative. It also dealt a blow to the Kremlin, showing its failure to protect its country's territory and shattering Putin's narrative that Russia is largely untouched by the war.
But despite initial successes, an attack on Russia could deplete some of Ukraine's most capable units and leave troops in Donetsk without vital reinforcements.
Attempting to establish a permanent presence in the Kursk region could be a challenge for Ukrainian forces, whose supply lines would be vulnerable to Russian fire.
Military analysts say that it is not yet clear what Ukraine's operational goals are and how many soldiers are in the attack on Kursk.
Michael Kofman, a military analyst at the US Carnegie Endowment, said that "it all pretty much depends on what Ukraine has in reserve to throw into the operation and how quickly the Russian Federation will organize to counter."
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