Jikuu Mahou de Isekai to Chikyuu wo Ittarikitari - Chapter 375 - Charming Fairy

The great journey of an ordinary martial artist.“Once your habit is tainted, you have no choice but to live as a dog forever. Do not turn the wolf inside you into a dog.”

Travel to the primitive world, open up wasteland and farm land, tame animals and fish, build houses…

Jiang Xuan wants to create a tribe of his own!

- Description from novelbuddy

This is a world where a king is the most powerful.

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.