Epic Of The Demonic Sage - Chapter 234 - An Unexpected Gain

An advertising director is reborn in 1988 Hollywood as an eighteen-year-old blond-haired westerner named Eric Williams.

Time flew by. Even though their graduation was a long time ago, after countless nights and passing through fleeting time, their story is still circulated around the quiet campus of University G. This story has many different versions, but there is one thing that everyone knows to be true. Back then, that ordinary girl betrayed the genius of the fine arts faculty and yet, his love for her still remained. For her, he nearly died in a fire. For her, he gave up his chance to study abroad. Years later when they meet again, he is successful with a new girlfriend in his arms and she is indifferent with a light and clear smile. However, unknown to anyone, her longing had begun long ago and even now flooded her thoughts…

- Description from Novelupdates

Prince Alexander Herald von Triesenberg was the fourth prince of the Empire of Triesenberg who was banished from the Empire of Triesenberg for the crime that he didn’t commit.On their way to the island where he would be banished, a powerful storm swept through and sank the ship. Alexander drowned and at the moment, he thought he died from drowning.However, when he opened his eyes, he found himself lying on the shore of a sandy beach and a floating interface before his eyes.

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.