COTE : There is Something Wrong With Hikigaya - Chapter 255: The Student Council is Absolutely Fair

Before the rebirth, Gu Qingyao wanted to marry him but did not dare to marry. After the rebirth, Gu Qingyao, with the space materials in hand, all day planning to marry him with a huge dowry.

In an alternate world, a demon disrupts dynasties, harvests souls, and refines a banner of ten thousand souls.Under the heavenly tribulation, his body and soul are destroyed, but the Ten Thousand Souls Banner protects his undying spirit. Unable to possess a body, he's countered instead.A laid-back young man in society, wielding the Ten Thousand Souls Banner, roams the human world.With the Ten Thousand Souls Banner in hand, I refine a Golden Core with good deeds.A slice-of-life story with no ambition for conquest, helping the departed fulfill their wishes, gaining merit to repair the Ten Thousand Souls Banner, and enjoying a laid-back life.

Go back to 2000.

Lin Feng didn’t want to disturb the situation, he just wanted to protect the things he cherished.

However, there is no need to explain the open life.

Since it’s all over again, there’s no turning back when you open the bow!

- Description from novelbuddy

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.