[mtgp1000]

>Roman Empire, British Empire, Ottoman Empire, Japanese Empire, Mughal Empire

Imagine, for a moment, that each one of these had nukes. What's the probability they'd use them to make a point as an aggressor/opressor? Even risking MAD?

[renewiltord]

Probably the same, with the same knowledge available. If you just gave a Roman Emperor unlimited use of nuclear weapons, sure, he might go ham. He didn’t even know the extent of the world. But you don’t get nukes without awareness of what a nuke is.

Given everything, I think the highest likelihood outcome is that they behave similarly.

[ceilingcorner]

Considering the actions of all of the empires I listed, I'd say: absolutely likely that they would use any and all weapons available.

Also: MAD only exists if you let your opponents acquire nukes too.

[atlasunshrugged]

The US definitely would have used nukes, especially in Vietnam - I believe that the reason the US President is the one with the nuclear suitcase and who it the end decision maker (probably something more people are nervous about now) is because when Truman learned about the nuke project (I'm not sure he had been aware of them until he became president) and used them he was afraid the military would use even more. Former SecDef Perry does a lot around nuclear nonproliferation and has good free courses, a podcast, and a book https://www.wjperryproject.org/