As the Ukrainian military broke through Russian defensive lines, it recaptured major cities in the matter of days. On September 7, the second day of the counteroffensive, the Ukrainian military advanced over 20 kilometres (12 mi) into Russian-held territory. The next day, Ukraine recaptured Balakliia and Shevchenkove as Russian forces withdrew and fled. On the 9th, Russia began announcing for evacuations in nearby areas as the Ukrainian military continued its advance. The next day, Ukraine retook the key cities of Izium and Kupiansk, securing access to the Oskil River. By the 11th, Ukraine has successfully advanced up to 70 kilometres (43 mi) from the pre-counteroffensive front line. In turn, Russia's defence ministry announced the withdrawal of all forces west of the Oskil.
The pace of the counteroffensive then began to slow, but continued until early October. By September 13, the Ukrainian military continued advancing and crossed the Oskil River. Fighting continued over the next two weeks as Ukraine advanced and recaptured smaller villages. By September 26, Ukraine retook Kupiansk-Vuzlovyi on the east of the Oskil, securing its presence on both sides of the river. By late September, Ukraine began encircling the city of Lyman before capturing it on October 1.
During the offensive, Ukraine retook over 500 settlements and 12,000 square kilometers of territory in the Kharkiv region.[20][21] This blitzkrieg disrupted Russian supply lines and significantly hindered its operations in the war.[22] It also served as a morale boost for Ukraine, as it continued to receive Western military aid during the war.[23]
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