Hyperdimensional Universe: I have Three Thousand Ultimate Talents - Chapter 74 - : 74: Sword Eight, The Strongest Mind

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.

After dying prematurely from an incurable disease, Yuka Hikano finds himself in a mysterious realm filled with endless doors, each concealing divine gifts from powerful deities. He is not alone—others who have met the same fate of death stand beside him, unaware of the trials that await.They are put through various tests and eventually transmigrated into different worlds. But these worlds are nothing like the Earth they once knew.For Yuka, however, this apocalyptic world feels eerily familiar. It is a realm of endless war, devastation, and chaos—a world he once played in a game. Certainly not the kind of place one would wish to be reborn into.From infancy to adulthood, he must gather strength, knowledge, and allies to survive the horrors that lurk ahead. But when he awakens a system granting him a power beyond imagination, he soon realizes that blessings can also be curses.[You have gained Infinite Mana.]Infinite Mana...?What could possibly go wrong?

Liu Ergou grew up in the village and studied medical skills with his grandfather. After his grandfather died, the responsibility of treating the villagers falls on him. But an accident bestows upon him an inheritance from his great-grandfather, which sets him on the path to invincibility!

After the soldiers’ mercenary group where he used to work had been utterly destroyed, Loren, who survived the disaster, decided to walk the adventurer’s path as a way to make a living. However, for Loren who had no acquaintances and nothing but an empty pocket on him, receiving a single quest seemed like a faraway aim. So, as he was contemplating about what he should do next, another adventurer called out to him.