The IS-2 was issued to Guards Heavy Tank Regiments from the start of 1944. The first unit equipped with them to see action was the 11th Guards Independent Heavy Tank Brigade in April in operations in the southern Ukraine, following the successful encirclement and destruction of German forces' in the Korsun-Shevchenkiovsky area. In 20 days of fighting, the 72nd Independent Guards Tank Regiment lost only eight IS-2s, whilst inflicting great loss on the enemy, although Soviet claims of 41 Tigers and Elephants is excessive and probably the result of mistaken identity. During this period of action, one IS-2 withstood five direct hits from the 8.8cm (3.46in) gun of an Elephant fired from 1500-2000m (1640-2187yd). The vehicle was eventually knocked out by another of these vehicles at 700m (765yd). The loss of other vehicles to fire and engine damage serves to highlight the point that even the most heavily armoured tank still has areas of vulnerability.
One of the IS-2's most notable engagements took place during the fighting in August 1944 to establish a bridgehead across the river Vistula around the town of Sandomierz. This was the first time that the IS-2 had come up against the fearsome Royal Tiger. During the engagement on 13 August, the 71st Independent Heavy Tank Regiment's 11 IS-2s blocked an attack by 14 Royal Tigers of the 501st Heavy Panzer Regiment. Engaging at 600m (656yd) coupled with skilled tactical handling saw four Royal Tigers destroyed and seven damaged, for the loss of three IS-2s and seven damaged. This was a very creditable performance, although post-battle analysis again revealed that the IS-2's armour was vulnerable up to 1000m (9144yd) because of faulty casting.