@Moonstone23 

I have a few more if you'd like:-

The Holy Roman Empire - guy is reborn into the last emperor of Austria and then builds up from there. 9/10, great but sometimes reads like a world history textbook.

Black Corporation: Joseon - 10/10, hands down one of  the best Kingdom building novel I've read upto date. MC is reborn into eldest son of a prince ( later king) and is a real genius.

I became the first prince- 10/10, A magic sword finds itself occupying the body of a tr*sh prince. Great character growth.

Living leisurely in tang Dynasty - a little prince's life. Pretty slice of life here and the MMC is never the emperor but he is pretty influential.

A king is born on the road. 8/10, a princess is reborn and strives for the throne. Love the FMC in this one 

Children of the holy emperor - 10/10, great story, very heartwarming.

Release that witch - 7/10 Nice if a bit cliched. 

Napolean in 1812- 9/10, is incomplete, otherwise would be 10/10. About Napolean from an alternative reality trying to clean up the mess his counterpart left.

Mediterranean Hegemony of Ancient Greece - 8/10, same author as the holy roman Empire, didn't like it as much because of the harem.

Fox of France - 7/10, a dude transmigrates into Napoleon older brother and interacts with famous historical figures. Don't think he became emperor tho.