The Spare's Second Chance in Apocalypse - Chapter 20: Ch : Smooth Preparations- Part 2

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.

He is the ruler of the mercenary realm, an overlord that gives headaches to the leaders of any country! For the sake of his friends, he’s willing to sacrifice himself; for the sake of his family, he does not hesitate to spill blood! He is a dragon, one that soars above even the highest of heavens. He’s a power that advances triumphantly through unstable situations, stirring up both the winds and the waters.

One sunny afternoon, Kyle finally received the admission notice he had longed for and came to Hogwarts, a prestigious school with thousands of years of history.

Here, Kyle lived a very fulfilling life. In addition to studying every day, he would also use his spare time to plant vegetables and flowers, or go to a dark underground chamber to provide psychological counseling to a small animal that had been abandoned for thousands of years. .

Dumbledore: Kyle is a good boy who is upright, brave, kind and sincere.

Professor McGonagall: The Headmaster is right, Kyle never breaks school rules.

Snape: Ah, yes, yes…

Quirrell originally thought so, but until one day, he pushed open the trap door and jumped into a room full of biting cabbage…

- Description from novelbuddy

Kawaki, who was born in the dragon vein of a planet (Altana), first met Umibozu who was traveling in the universe, and his girlfriend, Kouka.Later, he came to Earth by accident and met the teacher who affected his life —Yoshida Shouyou.He also met a group of friends. The most conspicuous among the group of friends is a fool with silver hair and naturally curly hair, a short man with purple hair, and a little devil whose catchphrase is “Not Zura, it's Katsura!”Gintama Doujin, not transmigration.