A very powerful tier 7 heavy tank but also a very unforgiving tank that requires a lot of work and effort to compensate for its many weaknesses. But if you invest a lot and are good enough, it can be a clutch machine.

Cons:
- Unreliable armor: Even though on the profile you can see that the IS has many well-angled armor parts, particularly on this tank you are more armored than the standard IS thanks to the completely angled frontal hull, and it may save you from some bad RNG round, you are, however, not well-armored like O-Ni, T29, or the Tiger 2 C (Which I consider to be very OP) due to many weak spots, especially the gun mantlet which only has 100mm of thickness, and experience people will immediately shoot at this place, kill your gunner/commander and possible took down the turret as well. Worse, clicker can critically hit you due to your large profile and thinly-armored part on the tank surface, especially the commander hatch.
- Terrible gun dispersion and accuracy: 0.40 with 100% crew and BIA, needless to say, you are not a sniper. Your gun will bloom like a nuclear explosion even when slightly adjusting your tank angle or barely moving your aim. This tank will teach you how to use the automatic gear function (R and F by default) to its maximum potential
- Bad view range: Basically, any TD hiding behind a bush is invisible to you so you better hope he made a mistake. If they use the double-bush mechanic, just hide, don't bother.
- Horrendous penetration value: This applies to all IS variants. 175 standard and 217 gold are not enough to combat against even some tier 7 and many tiers 8, even medium ones. You can't reliably penetrate the frontal hull of IS-3, Emil I, and if your luck is down bad enough, you can bounce off even your biggest threat which is any other tier 7 heavy, especially the T29, your biggest threat. Back when Wargaming has not nerfed HE, you can use it to fight against higher tiers. But now, don't be a hero, run and wait for their misplay.
- Average mobility: You would think with all these problems, surely mobility would be something this tank has right? Nah, it is OK at best. Heck, even the T29 is faster than you while being better than literally every aspect.

Pros:
- 390 Alpha damage: The biggest W for this tank and the sole reason why you play it. You can basically 2 taps most tier 5, cripple tier 6, and punish tier 7 and 8 for their mistake. I cannot stress this enough, the only reason why you want to main the IS is for its alpha. That's it.

How to play: This tank relies a lot on whether or not it is a top tier or not. First, install XVM. If the enemy is mostly red tomato, play aggressively. If not, play safer and play the waiting game. If you are top tier, play even more aggressively and toxic. Try face-hugging your opponent to make them panic. As long as you can fool them away from looking at your gun mantlet, you are good to go. If you are bottom tier, play more passively, your gun stands no chance against the frontal hull armor of most tanks in this matchmaking, so you need to play extremely well and strategically on the mistake of your enemy.

Recommended equipment: Vent/Gun Laying Drive/Improve Aiming. It may seem weird not using rammer or rotation but trust me, the entire point of your gun is to bonk people, not hit them repeatedly like the Tiger. Since it is already hit hard enough, but the accuracy is very bad, all you need to do is simply compensate for this tremendous downside.