Preface: This is a theoretical question, not one associated with any current events.

Question: Is it possible for the US and Russia to fight in a country like Iran without the use of nuclear weapons or proxies? How?

My Answer: I'm uncertain of where to go. On one hand it feels like it could be possible, but my concern is that it would be just too enticing to attack production/manufacturing in the US/Russia via airplane to contain the combat. Further, I assume each country knows this, so direct fighting in a 3rd parties country is avoided because it would lead to direct confrontation.

There's also further issue for Russia in that the US's ability to project power is unrivaled. They would be hard pressed to put boots on the ground anywhere but Alaska.

Russia knowing this I think means any direct conflict means push the red button.

Extra Credit Question: If at some point a country gets the ability to prevent MAD, do they use it to conquer the world?