Citadel for All: The Only Unit Angel at the Start of the Game - Chapter 513

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.

“Will you marry me, Anais?” The male lead proposed to me. “What about Selena?” “Selena doesn’t matter. You’re the only one I’m interested in now.” Even without a hint of interest in the female lead. “I’m sorry, but I…” Before I could even utter my refusal, the refreshing sound of coins rang in my ears. [asdf has donated 100 points!] Accept and get ten thousand points “Shall we go pick out a ring first?” Forget about conscience; if it’s fun, that’s all that matters.

Beneath the peaceful façade of the modern world, an undercurrent of shocking crimes roils in the underbelly of society.

Euri was quite passionate about wanting to become a perfect corporate slave.But after being forced to explore the sentient game infesting his miniscreen, Euri realized that he had stumbled upon an opportunity anyone on the planet would kill for. While the entire human civilization on Planet Nen struggled to deal with the superior lifeforms plaguing the extraterrestrial planes beyond their world, Euri could compete with them all for power by just playing this game!A side-gig that didn’t conflict with his dream of climbing the corporate ladder—how generous can fortune be to bequeath this opportunity to him.Transcending the spatial laws, transcending human notion of cultivation, transcending the rules of Cosmic Development Bureau, Euri began a series of crazy experiments that could perhaps destroy the millennia-spanning schemes of the most advanced civilizations controlling the macrocosm.When interrogated about this fiasco, Euri answered the way a perfect corporate slave should. “Full credit for this goes to my boss, who provided me with the opportunity...”