In February 2025, amid a large restructuring within the Ukrainian military which introduced the corps structure above the brigade level, it was reported that the 3rd Assault Brigade would form the nucleus of a new corps. [10] [11] [12] [13]
On 14 March 2025, colonel Andriy Biletsky, commander of the 3rd Assault Brigade, officially announced the formation of the 3rd Army Corps under his command. [10] [13] [14] [15] The corps began operating the same month. [8] Several weeks after Biletsky's announcement, the 3rd Army Corps began integrating other brigades and units under its command. [6]
In May, Ukrainian military journalist Yurii Butusov [ uk ] wrote that once all the bureaucratic processes relating to the formation of the corps were completed, it would be able to deploy its forces to stabilize the Kupiansk and Lyman fronts. [16]
Operations
According to Butusov, on 4 June, amid an "extremely critical situation" on the front, the transition to the corps command system was implemented, and the entire 120-kilometre (75 mi) line held by the constitutent units of the 3rd Army Corps was formally placed under Biletsky's command. [17] [6] This included the areas of responsibility of two Ukrainian brigades where the Russians had managed to advance significantly during the first half of 2025. [17] Butusov and Ukrainian journalist Serhii Bondarenko have claimed that between June and late July, Biletsky improved the situation on the front, slowing down and repelling Russian offensives. [17] [6] Corps commanders said in August that after establishing its command over the front, the corps had managed to almost entirely halt Russian advances in its sector, preventing a Russian advance to the Oskil River. [2] [18]
In August and September, commanders said that the corps was conducting a "large-scale defensive operation" on the Lyman and Borova fronts amid a Russian offensive against the final Ukrainian defensive line in the northern part of the Donbass region. [6] [3] [19] Butusov and members of the corps' command have said that the 3rd Army Corps is positioned against Russia's 20th and 25th Combined Arms Armies, which are supported by units of the 1st Guards Tank Army. [17] [6] [4] This reportedly constitutes a significant numerical advantage for the Russian side. [6]
In August and September, [3] it was variously reported that the corps held between 120 kilometres (75 mi) [20] and 150 kilometres (93 mi) of the front line between the cities of Lyman (Donetsk region) and Borova (Kharkiv region). [21] [6] [18] Corps commanders have said that the corps holds about one-eighth or 12% of the total active front line in Ukraine. [2] [3] [19] In an August interview with The Times , Biletsky said that the corps was "motivated by a strong nationalist ideology". [2]
Ukrainian Ground Forces 
