Manga World: Bringing Steam Technology to the World of Sanctuary - Chapter 92: Evolution and Birth of Celine

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.

On that day, the fog blocked everything.

On that day, he became the captain of a ghost ship.

On that day, he stepped through the thick fog and confronted a completely subverted and fragmented world—the old order had vanished, strange phenomonoms dominated the endless seas beyond civilized society, and isolated island city-states and fleets of ships challenged the sea that had become the last ember of lights for the civilized world. All of this while the shadows of the old days were still stirring in the deep sea, waiting to to devour this world that was about to die.

But for the new captain of the ghost ship Vanished, there was only one question he had to consider first— Who knows how to drive this ship?!

Crossing to One Piece world, he became Roger’s younger brother.

Unexpectedly, Gol-D-Roger who was in his fifties had a teenage brother. But he was so weak.

Fortunately, at the age of sixteen, he actually found himself with a possession soul system.

He had attached to the master IP man, also to the White Phoenix and to Ge Nie with his strong ability of the Hundred Step Flying Sword.

If you think that he can only Purchase these? Then you’re wrong!

Pain, Itachi, Ichigo Kurosaki, as long as there is money, any soul can be Purchased.

- Description from Novelupdates

A s*ave boy, Ram, who assassinated an enemy commander to end a war.Jedrik, the great chieftain of the North.Demion, the prince of the South.Charlon, the duke’s daughter.The blood oath they forged plunges a seemingly ended war back into chaos.