Oskil River in the context of "Don (river)"

On 6 September 2022, the Armed Forces of Ukraine launched a major counteroffensive against the Russian military during the Russo-Ukrainian war. As Ukraine announced the start of the Kherson counteroffensive in southern Ukraine in late August, Ukrainian forces also began a second counteroffensive in early September in Kharkiv Oblast, in eastern Ukraine.

As the Ukrainian military broke through Russian defensive lines, it recaptured multiple cities in a matter of days. On 7 September, 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 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 Oskil Reservoir (Ukrainian: Оскільське водосховище; Russian: Оскольское водохранилище, sometimes translated as Oskol, Oskilske -) was an artificial lake on the Oskil River in Kharkiv Oblast, Ukraine. It was formerly known as the Chervony-Oskil Reservoir.

The reservoir was opened in 1958. Before it was drained, the reservoir's area was 130 km², with a maximal length of 125 km, a maximal width of 4 km, an average depth of 4 m and a volume of approximately 474 hm³. The purpose of the reservoir was to regulate water levels, to serve as a source for electricity, and to help the fishing industry.