Pros and Cons
Pros:
- Very strong turret armor
- Great tank for sidescraping
- Higher penetration, faster aiming and better accuracy with the top gun than IS-7
- Relatively high HP pool
Cons:
- Thinner frontal armor than most tier X heavies
- Rather huge and soft lower glacis
- Rather slow and sluggish
- Less mobile compared to the IS-7
- Driver dies from frontal shots rather easy
- Outrageous repair cost
Performance
It is a common tank to see on the battlefield for a very good reason; it has a decent amount of speed, good armor values all around and mounts a high-penetration gun. Many players view the IS-4 as a superior tank to the IS-7 because it does not have the weak rear armor that the IS-7 has. But like some machines of war, it finds itself in a "jack of all trades-master of none" position in that that while performing well, it does not particularly stand out in any one area. However, if played right, the IS-4 can be a feared and respected tank. The IS-4's somewhat weak point is its mobility. The turret traverse speed is average. It deals decent damage, and combined with its sloped armor, it is a well rounded tank.
You should carry your crew over from the ST-I so you have good crew to start with. First get Repair for all of them, because you don't want to stand in open where artillery can shell you. Then you should get Mentor for your Commander, because this skill helps the other crew get skills and perks faster. Your Gunner's 2nd skill should be Snap Shot, Clutch Braking for the Driver, and Safe Stowage for the Loader. Then you should train them all in BiA (Brothers in Arms). If you get high enough for another one then you can get Sixth Sense for the Commander, Designated Target for the Gunner, Off-Road Driving for the Driver, and Adrenaline Rush for the Loader.
Early Research
It's impossible to come from the ST-I without researching the improved gun, so it should already come elited.