Sanctuary: Safe Haven - Chapter 17: More! More! Training!

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.

The Pseudo-Holy Grail War of Snowfield is About to Begin!Moran, who has transmigrated into the Type-Moon universe, is determined to clear the game in one life!Waiting online, urgent!Ding! You have successfully activated the Life Simulator!• 【You drove out the foreign Olympian Machine Gods, took the hand of the Earth Mother Goddess, and founded a new nation and mythology.】• 【You are the Lord of the Millennium Castle, bestowed with the name Brunestud, and the beloved ruler of the land in the eyes of the Crimson Moon.】• 【You are the Final King of the Age of Gods, single-handedly preventing its decline and ensuring that Divine Age Britain endures to this day.】Behind this dazzling simulated life, Moran now faces—Arcueid: “Weren’t you supposed to pick me up at the Millennium Castle? Why are you here in the Holy Grail War?!”Artoria: “Enough! Come back to Britain with me!”Ereshkigal: “Moran! Who are all these women?!”As his ever-growing circle of admirers closes in, Moran realizes—This might just be the hardest “Kidney Grail War” in history.

He died. Not by fate, not by accident, but as collateral in a hunt between beings beyond mortal comprehension.And yet… death was only the beginning.Chosen by a mysterious entity known only as Echo, a sarcastic soul from Earth is offered a chance at a second life. Gifted with ten draws from a divine treasury, he obtains powerful treasures, a rare bloodline, and a mysterious system known as the Limitless System.But what begins as a straightforward reincarnation takes a twisted turn when two dragon inheritances—Thunder and Fire—collide within him.Reborn not as a man, nor as a beast, but as an unknown species—a fusion of human and two True Dragon Inheritences—he awakens in a scorched battlefield beside a dragon egg, unaware that his birth was witnessed by fate itself.After surviving the near-fatal clash of legacies within him, he emerges anew… no longer Zaroth, but Primus Xal’Zaryon Drakonis, a name that shakes the very fabric of mana around him.With his soul, body, and bloodline perfectly harmonized between human and dragon, Primus sets out into an unfamiliar world ruled by ancient clans, dangerous beasts, and kingdoms teetering on the edge of Eternal War.But power always draws attention—and with the secrets of his origin, the Limitless System at his side, and a destiny marked by a Primordial-level Mark of Fate, enemies will rise from shadows unknown.

When I woke up after being transported to another world, I am suddenly the antagonist? This script is wrong! I stole the other guy’s girl! I also have a super strong big sister! This script is even more wrong! There’s even an Overgod Space, along with the infinite worlds? I must be dreaming! Wu Ming calmly maintains his neutral expression and journeys ever onwards.