The villainous daughter of the Duke, needs a hero - Vol 2 – Chapter 12: The la Marche Brothers.

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

Because of his master’s wine, he had somehow become the husband of a cold CEO — I’m still a virgin, please be gentle. He was from an ancient sect and had both Buddhism and Dao cultivation methods. The youth Qin Wu stepped out of the great mountain once again, stirring up the winds and clouds in the city.

- Description from Novelupdates

In the year 241 of the 6th era, Constantinople was in turmoil.Emperor Constantine personally lead his army, which was completely annihilated. The pagan empire, riding on the wave of a great victory, annexed the entire eastern territory of the empire, and its military might pointed directly at the capital.The 17-year-old imperial princess Theodora ascended the throne in crisis, facing what was already a terribly damaged realm.Rome was about to fall.....................The wheels of fate spun wildly as a transmigrator appeared on the streets of Constantinople.“According to the original plot, it was only a matter of time before Constantinople would fall.” he pondered.“Perhaps I should first whisk away the empress.”(The book is categorized under game fantasy worlds, set in a magically altered Middle Ages, and another title is 'I Really Can't Lead This Team')