Ukrainian Army isolated part of the Kursk region, large number of Russian soldiers left without help

Ukrainian forces in the Kursk region blew up all three bridges over the Seim River, isolating about 300 miles of territory and cutting off Russian units there from the main forces.
As Forbes writes, from August 16 to 21, the Ukrainian Armed Forces destroyed three bridges - in Glushkovo, Zvannoye and Karyzh. The Russians tried to establish temporary pontoon crossings, but the Ukrainian Armed Forces did not allow them to do so - Ukrainian drones intercepted some of the bridges while they were still in transit, and M30/31 missiles fired "hundreds of grenade bombs" at one of the pontoons, Forbes writes.
As a result, after six days of river campaigning, a huge section of the Kursk region - and all Russian troops located there - was effectively cut off from land supplies and reinforcements.
"That the Ukrainians are so determined to isolate the Kursk region to the left of the Sejm is a strong signal that their next move could be a ground attack through the Sejm into the region they just isolated," Forbes writes.
According to Ukraine's Center for Defense Strategies, the Ukrainian Armed Forces are seeking to "get ahead of the enemy in the operational deployment of forces in this direction," and the destruction of bridges is key. Russians can no longer easily reach this part of the Kursk region, unlike Ukrainians, who can get to the area by crossing the border.
And the Russians also cannot resupply and reinforce their troops between the Sejm and the border with airlifts - the Ukrainians have made the skies over the Kursk region extremely "unfavorable" for Russian helicopters, shooting down several of them since the invasion began on August 6.
While the Ukrainian incursion in the western Russian territory of Kursk seems to be steadily gaining ground, the Russians are close to achieving a goal of their own in the Donbas after they took the town of Niu-York and advance on a key transport junction of Pokrovsk.
In the Kursk area, the Ukrainian forces are trying to seize Korenovo. The fall of this city would allow them to strengthen their defences in Russian territory and build a coherent "buffer zone" to protect Kharkiv and other northern cities.
Such a buffer zone, stated by President Volodymyr Zelenskyy to be the incursion's main goal, would be a major operational success for the Ukrainians.