Strongest Survival by Otome Game’s Heroine (LN) - Vol 3 Chapter 14: Madman

After sleeping for over two thousand years, she woke up, only to find she had lost everything and was even going to be sold at an auction by her father.On her way to escape, she met him by chance. He was so handsome and adorable, like a cute little dog. So they got married in a flash.Later, she accidentally met the first interstellar commander whose mask had fallen off. Rumor has it that anyone who sees his true face will die. She trembled with fear, “What a coincidence! You look exactly like my husband!” He said, “I am your husband.”From then on, he clung to her every day, wanting to have a child. She felt regretful: He looks like a wolf now! She misses the little puppy she used to have so much...

I Became Hades, the God of the Underworld from Greek and Roman Mythology

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.

In the Year 350 of the Anping Dynasty, humans were faced with a huge crisis. Earth was invaded by monsters from another dimension. Fortunately, Su Yu awoke a power where he possessed a scripture that allowed him to contain everything in existence. With that power, he was able to face the coming apocalypse.