Maou Gakuin No Futekigousha - Chapter 9: Aptitude test

The rivers and lakes carry wine with swords, the waist is slender and the palm is light.

The young man carried a long knife on his shoulder, and hung wine on his waist, striding forward, but the rivers and lakes in his heart were vaguely visible.

Turning a page in the book of troubled times, the rivers and lakes have been raining nightly for decades.

Looking back suddenly, the world has been shattered.

- Description from novelbuddy

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.

Earth Online – a virtual MMORPG that takes place in the future year of 2190 – a game that everyone will bet their futures on. Set in a map that is ten times the size of real-world Earth, players battle for supremacy in the first game to feature personal adventure, territory construction, and grand warfare. For every death you experience in the game, your level would drop back to zero. Ouyang Shuo, an above average player, suffered the ultimate betrayal. For merely a piece of equipment, his sworn brother betrayed and backstabbed him. This time, after he reincarnated in the game, Ouyang Shuo swore to exact vengeance.

However, in an unexpected turn of events, Ouyang Shuo found himself back five years before the betrayal – right before the launch of Earth Online. This time, armed with the knowledge from his past life, Ouyang Shuo would venture upon a new path.

How to perfectly complete quests? What historical battle maps would appear? How should one build up their territory? Utilizing the experience from the predecessors of his last life, Ouyang Shuo makes his bid for the top against all odds. Follow his journey as he seeks to lord over the world!

A different kind of tale that blends historical characters and virtual reality gaming, with heavy emphasis on kingdom building and warfare.

- Description from Novelupdates

After being struck by a crazed driver, Eden found himself reincarnated into another world as the last heir of one of the three most powerful clans.Immediately after birth, he was declared a powerful god known as 'Doom'. However, he soon realized that he had been reborn into a world from a novel he had never read, only seen advertised.In this world, evil souls and exorcists existed in secret, hidden from the citizens who lived in ignorance of their presence. Exorcists were born to rid the world of evil souls, maintaining the balance of the world.Eden was born with the power of Doom, and his eyes were meant to be covered at all costs, for anything they gazed upon would meet its demise.Determined to control his power, Eden struggled but failed. Everything changed when the inevitable finally arrived...[Ding! You have obtained the Doom system]A system that shall create the pact for him to tame his power and successfully defeat the evil souls.[Special ability! Host has the special eyes of doom from birth][Ding! Reversing weak aura into......]Eden was reborn with the most chaotic power and it is only a matter of time before we know what this ability shall cause upon this world.