SorryImJustDiamond

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!!!

Donation link: https://ko-fi.com/sorryimjustdiamond

PS. Cover not mine, I just found it on google. If you are the owner and want me to take it down, then you can reach me in the comment section.

Reincarnated as an Imperial Prince

Meanwhile, at the same time, one hundred and fifty meters below the position of the first Imperial Yamato Fleet, a copy of the Collins Class diesel-electric submarine, His Imperial Ruthenian Majesty's Ship Morzh Class Submarine stealthily trailed the enemy fleet at a speed of three knots

The submarine was under the command of Captain Vasily Aleksandrovich Arkhipov. They are tasked to trail the enemy fleet covertly all the while informing the Ruthenian High Command of their whereabouts.

The Yamato Empire's current sonar capabilities couldn't detect any noises produced by the submarines except for the wailing of the whales or the fish wagging their tails. It was all thanks to the Stirling engine integrated into the ship, making the ship almost quiet and vibration free, making it hard for the enemy sonar operator to find them.

Blow Them Up