Steel, Guns, and the Industrial Party in Another World - Chapter 407: Farewell Banquet

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.

A mysterious teenager who had lost his past, awakened in Tianlong Continent. Mistaken as the Ye family’s Son, he used this identity to observe this chaotic world and to search for his past self, but only to find an inevitable and terrible fate, therefore he indignantly laughed at his destiny, and revealed his prowess to rule the lands under the heavens.

Since then, the air and the clouds moved with his hands, and even thunderstorms were subject to his palms! He, as the fairytale’s main character, had shocked the people of Tianlong Continent with his legendary prowess and intelligence, but the extent of his powers were still unknown.

- Description from novelupdates

A master assassin transmigrates into an interstellar era.

Other players were responsible for competing in the e-sports arena, while he was responsible for stringing up and beating up the other players.

His sword was hidden during the peak of day, and he was a gentleman who arrived in a flash of light;
As a vanguard of the eternal night, he was the variable between life and death in the world.

“As you know, the Star League’s difficulty levels are arranged in this way:
Paradise < Simple < Normal < Difficult < Nightmare < Hell < [Tyron Odin]”

- Description from Novelupdates

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...