My little initial Googling on the in service dates for the IS-2 heavy tank suggested it could have been used at the end of the Korsun Pocket action. However, Richard Naylor was kind enough to volunteer some feedback and suggested that the IS-2 wasn't in action yet. So I've had another dig through my books and internet sources.
Tanks encyclopaedia says:
"Their first action was in February 1944 at Korsun Chevchenkovski, Ukraine."
Flames of War agrees:
"It first saw combat in February 1944 during fighting around Korsun-Chevchenkovski pocket."
However, Militaryfactory.com says:
“First combat action was recorded in April of 1944 when IS-2, operating under the banners of the 11th and 72nd Independent Guards Heavy Tank Regiments, fared well against German Panther tanks - for all intents and purposes, the legacy of the Joseph Stalin tank had begun.”
The Archive Awareness blog has signal to Marshal Konev on the first arrival of IS-2s with 2nd Ukrainian Front, the start of which reads:
Military Council of Armoured and Mechanized Forces of the Red Army
April 1st, 1944#481904SS
To the commander of the 2nd Ukrainian Front, Marshal of the Soviet Union, comrade Konev.
The heavy IS and ISU-152 regiments sent to your disposal contain the first batch of tanks and SPGs of this type.Both the tanks and SPGs have a series of small technical omissions. In addition, there is not yet sufficient experience regarding their use and application in combat.”
Peter Chen says:
"The IS-2 heavy tanks entered service in Apr 1944."
Meanwhile Mitch Williamson's Soviet Hammer blog says:
"By the end of 1943, the Kirov Factory had produced a total of 102 IS-2 heavy tanks and they were used for the first time in February of 1944 at Korsun Shevkenskovsky."
Whilst at the same time he gives the production dates as "April 44 to June 45"!
I think I'll park this for now. After all it's all irrelevant if no one brings an IS-2 model!