Harry Potter: A Certain Ancient Rune Professor of Hogwarts (TL) - Chapter 688

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.

This is a prequel to the anime movie To Aru Majutsu no Kinsho Mokuroku – Endymion no Kiseki.

Just before the completion of the Academy City space elevator “Endymion”, the main characters Kamijou Touma and Index encounter a level 0 girl named Arisa. The Magicians are after Arisa, and they attack Academy City. A female leader named Shattoaura leads a unit from Academy City against the attack. Kamijou and Index learn from Stiyl that Arisa is key to a brewing war between the sides of Magic and Science. When science and magic cross paths, the story begins with Endymion as its stage!

Traveling through the world of cultivating immortals, Su Yu became a collateral child of an ordinary cultivating family, with nothing but handsomeness, mediocre cultivation talent, and mediocre life experience.

Fortunately, Su Yu brought the game proficiency panel he played in his previous life, ignoring all restrictions such as spiritual root comprehension, as long as he practiced from nine to five to accumulate proficiency, he could improve his strength.

If you live ten thousand years, you can become a fairy or a ancestor!

The Tianjiao of the Zongmen and the powerful ancestors are just passing away, only cultivating immortals… oh no, only the proficiency is eternal!

- Description from novelbuddy

Ling Lang is thirty-two years old and an A list movie star. He is also the youngest to become the king of the silver screen. Known for having a cold and aloof disposition, people nicknamed him king iceberg of the silver screen. His biggest secret? He is a masochist down to his very bones.

- Description from Novelupdates