Divine Lucky Star - Chapter 180: The Mysterious Cave

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 getting hit by a car, Nolan thought death would bring him peace. But instead of resting in heaven, he wakes up in a world of gods and power.Reincarnated in the Academy of Heavenly Descendants, Nolan now finds himself surrounded by the heirs of mythological deities—each wielding divine power beyond imagination.But there's a problem: the body he reincarnated into is cursed.Without the ability to cultivate Divine Essence, Nolan is labeled as worthless, an outcast in a world where strength means everything.Just as he’s about to lose hope, a voice echoes in his mind:[Congratulations, Host Has Awakened The God King System!][Initial Bloodline Scan Beginning...][Scan Completed][Host Has Awakened the Power of Kratos, the God of Strength and War!]Equipped with a system that enables him to contract thousands of various mythological bloodlines, Nolan journeys across the limitless planes of existence, searching for the absolute power to achieve his ultimate goal—freedom!A path many have embarked on, but none have succeeded.

Three thousand years ago, gods and Buddhas disappeared all over the sky, and the inheritance of practice was broken. It was not until the ancient civilization was destroyed that spiritual energy recovered. Ten thousand races took advantage of this to invade.

Five hundred years later, the human race gradually rose up and began to fight for control of the land of China, and counterattacked all races.

Three hundred years later, Fang Yi, the Lord of the Great Dao, slaughtered all clans, destroyed all the heavens, stepped out of the myriad realms, and fought against the Dao of Heaven.

In desperation, Fang Yi sacrificed blood to eight hundred small worlds, reversed time and space, and was reborn nineteen years old.

In this life, he wants to live a more relaxed life, perfect his Dao Xin, and conquer the Dao of Heaven again.

- Description from novelbuddy

Han Yun was spoiled from childhood.

He survived past his emperor dad and crown prince elder brother, and became an emperor.

He didn’t know how to govern the country, but he was lucky—there was a Grand Preceptor who “assisted” him, spoiling him even more than his father did.

After just a few years, this puppet emperor died. When he awakened, he had transmigrated into the modern world, becoming a third-rate model struggling alone without any loving parents.

Just when he thought he had become a little cabbage that nobody wanted and no one would ever spoil him again, a certain ancient monster of a Grand Preceptor who had lived 1,000 years appeared again… and looked to be doing quite well for himself.

The utterly impoverished little emperor had tears in his eyes: “Beloved subject! Zhen (royal We) have missed you so much!”

Grand Preceptor: “Your Majesty, this minister has waited for you for a thousand years.”

- Description from Novelupdates