The Soviet Flame-thrower has always been a powerful asset to any Red Army breakthrough unit. They pave the way by burning out enemy emplacements and preparing the way for the infantry assault.
In Flames of War
Use Flame-thrower teams to Pin Down the enemy before your troops crash into the assault. They each have a high ROF (4!), which will help burn out enemy teams and allow your following troops to mop up the remaining resistance. It is hard to imagine reasons why they should not be included in every Soviet force!