Substitute Bride: Utterly Pampered by Her Billionaire Husband - Chapter 7: Mrs. Crawford Who Supports You and Me

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.

She spent the night with the man who destroy her country, fleeing with their child in her arms. With that, she believed their relationship had come to an end. “Even if he’s another man’s child, even if he’s not of my blood, or even if he’s the child of a bastard, I’ll raise him as my own.” Until he came to her with eyes as ferocious as a beast. “Don’t even think about running away using the boy as an excuse. I’m still struggling to control the urge to crush the little creature that took you away from me.”

“I beg you, please teach me how to pick up female angels!!!”
Pleaded the twelve-winged angel.

“Teacher!! How can I fool more people into my sect?”
Asked a devil in the devil world.

“Do you know how to save the family cat that died last night?”
Someone in the sky is too embarrassed and asks me quietly.

“All the angel, all the big deity, please I am not God, I am really just a summoner….”
I said painfully.

This is the story of a poor boy and how he becomes the greatest summoner who dominates the six worlds because of an accidental acquisition of Dimension.

- Description from Novelupdates

Mortimer Zhu is an extremely unfortunate high school student who accidentally enrolls into an academy of a dubious nature, where it is the norm to jump in front of moving trains, get dismembered during orientation, and crushed by vindictive bouncing classrooms. Can he stay alive or will he die from the rigors of school? Why have evil spirits suddenly acquired a taste for his flesh?

- Description from Novelupdates