One Piece: Human God - Chapter 10: Yukiryu Island IV

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.

What is a Daoist Master? One that is imageless in ten directions and vanishes in the six paths; unrestrained by the three realms and the five elements.

Medieval times, warring knights, dragons, demons, gods, pirates, behemoths...Barbaric, ignorant, backward, numb, starvation widespread, people unable to make a living...Damn it! Punch to explode this era!!Reclaiming wilderness, farming, bridge building, road paving, coal mining, excavating minerals!Leveling up, recruiting apostles, forging an army!Barrage troops! Pushing horizontally!Quack! My steel torrent is invincible in this world!!Roman: “I am your destiny! Kneel before me!”So, you were supposed to farm, but somehow you ended up establishing a vast empire and becoming the emperor?