Battle of Kuuterselkä is correct.
First picture was to display the defensive line of VT-line. Picture was taken near Kuuterselkä, so it was quite accurate.
Second picture showed the biggest clue which would have solved the whole deal right away if you knew what to research. Sturms were deployed into battle for the first time during Kuuterselkä counterattack during the night of 14th-15th of June 1944. This particular stug in the picture was destroyed during this battle. If you would have searched the web for the vehicle (PS.531-1) you would have found out the battles in which it took part. And as it only took part in one battle and was destroyed in it, it was a dead giveaway.
Third picture shows finns leaving the battlefield, defeated. As the russians punched a gap to the finnish defenses and kept pouring in at Kuuterselkä, the Sturm counterattack accompanied by finnish jägers tried to contain the breakthrough and therefore stop the attack. But the enemy had expanded their bridgehead all the way to Kivennapa (this is why I said you are close with your answer) and the breakthrough was in no means of containment anymore.
So indeed, the battle was about the breakthrough of VT-line at Kuuterselkä which then expanded to Kivennapa, Vammelsuu and Sahankylä.
Other hints;
- Well T-34/76 was the main battle tank of the Red Army during the battle. Of course, this is rather general hint. But it was to aim those who wanted to guess into the way that this battle involved a lot of tanks, which it did.
- Battle continued during the nighttime as said above. Finnish counterattack to maintain the breakthrough happened during the night.
- World Record was one other "free pass" to this game. As it was the battle where Sturm gunner Olof Lagus scored the World Record of 4 enemy tanks destroyed within 30 seconds.
Also, those who saw Tali-Ihantala movie should be familiar with this rather awesome scene from the start of the film where the finns counterattack Kuuterselkä with Sturms.
Fuch's turn.