Strongest Survival by Otome Game’s Heroine (LN) - Chapter Volume 3 14: Madman

Rainer, an amateur arcanist and college student, sought to create a new spell far surpassing the magic of the few he inherited from his grandfather. Yet the interference of an unknown event during the casting of his spell led him to be thrown through space and time.

The Main Character, Watari Karito, is a veteran player of a Military Shooting VRMMORPG.

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.

After crossing, I also got the superhuman… twisted fruit.

This devil fruit was brought into full play by him.

Distort gravity, distort space, distort time.

Fight for hegemony in the new world and become the new emperor.

The top war choice is to completely evolve this epic battle into his stage.

Luo Chen declared to the world:

My time has come! !

- Description from novelbuddy