I Became Stalin?! - Chapter 44:

Quinn Winter is a young man from another world. One day, he is suddenly chosen to become the new Demon King. But the Demon Kingdom is in big trouble – it's losing a terrible war against the human kingdom called Gran'le.To help his people, Quinn comes up with a risky plan. He will sneak into Gran'le and learn their secrets. But things don’t go as planned. A powerful noble sponsors him, and he ends up joining Heavenward Academy, the top school for training future heroes.At the Academy, there's a big challenge called the Selection. The best students become Paladins – magic knights who fight demons. Quinn doesn’t want to become a Paladin. He is a demon king! But now, he’s stuck in the Selection… and if he wins, he’ll become the very thing he’s supposed to destroy.He started the day badly. Now, things are getting even worse.

Yeon-woo had a twin brother who disappeared five years ago. One day, a pocket watch left by his brother returned to his possession. Inside, he found a hidden diary in which was recorded “By the time you hear this, I guess I will be already dead….”

Year 24XX. With several hundred years of improvements, virtual reality has become more mature. It had gradually become humanity’s second world. Socializing, working, studying and other everyday things could all be done while sleeping.

Along with the rise in virtual reality systems, virtual games also developed successfully. Additionally, with the vigorous support of the government; every season, games continued to be born, be changed, competed with each other, and be reborn.

Ye Cang is a black bellied, underachieving, 2nd year student at a city college. He appears to have been cured of his albinism yet his story is still full of mystery. In the game ‘New Age – Conviction’, he began walking the path of a professional gamer. An all-rounder ranger, dark cooking, with a nasty disposition, willing to do anything. He’s slowly creating his own legend.

“Actually… instead of games, I prefer cooking and dramas” – The White Emperor

- Description from novelupdates

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.