Beware Of Chicken - Vol 1 Chapter 41: Tick Tock Goes The Clock

I reincarnated as Luna, a supporting character who is accused of ruining the heroine and hero’s relationship, and is mu*dered. I’m not interested in someone else’s man, but the heroine’s friends bully me every day. “Why are you trying to get close to someone who’s already taken?” “That’s right, please stop! Why are you doing this?” “Stop doing such terrible things!” So Luna decides to announce it in front of everyone. “I don’t want someone like Fersen even if you beg me to take him so stop bothering me. I’d rather date Anthes Vincent, who’s rumored to be insane.” And soon she meets someone who she never expected to meet…… “I heard you have an interest in me? The truth is, I do too. Is it a coincidence?”

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.

Civilization is destroyed and records lost. Only Dudian survives in a cryogenic sleep. Three hundred years later, Dudian wakes up and must become Dean to survive. Who can he trust in this world overrun by monsters without and within?

- Description from Novelupdates