Chaos Warlord: Reincarnated in Eldrich with the Devil System! - Chapter 317 314: New Rule 2

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.

One day, a silver-haired goddess appeared before him.“Heaven-Defying Star. The one who goes against fate. The sole savior of a world doomed to end—”What the hell is this woman even talking about?“You must be the Regressor.”“… What?”No, I’m not.

There are all sorts of lunatics in the world:Self-centered, reckless, psychotic, impulsive, obsessive, and pe*verted.As far as Suin knows, that man embodied every single one of those traits—an obsessive, pe*verted psycho.And now, that lunatic is back.“Finally, we meet.”“Adult Lee Suin.”He didn’t even try to hide the sticky hunger in his gaze, like a starved lion finally spotting its prey.“A job reassignment?”“I want Lee Suin to help me.”Chairman Woo Ilhwa, unaware of his son’s true intentions, reassigns Suin, his chief secretary, to serve as his son’s personal secretary.This forces Suin into close proximity with the man who’s been preying on her from the shadows.“Wait for me, Lee Suin.”During his eleven years of exile, Jaehee had dreamed of one thing:A proper relationship—not as a restricted minor, but as a full-grown adult.A relationship where he could take what he wanted, whenever and however he pleased.That’s why, even though Suin was as rigid as a steel rod, his sly persistence ignited the spark within him whenever he faced her.“What do you want from me?”“You.”“Lee Suin.”But it seems Suin has been flirting with some bastard behind his back, and Jaehee’s jealousy and obsession explode.“Don’t take a single step.”“Unless you want to see me go completely insane.”What nonsense.You were already insane to begin with.

There are a lot of things wrong with Liv Brodbeck. She’s too small, for one thing. When she works in the castle kitchens with her mother, she can’t carry a sack of flour or roll a keg of ale. Baron Summerset’s chirurgeon says that she has brittle bones, so she isn’t allowed to wrestle or sword fight with the other children. Even sledding downhill in the winter brings the risk of breaking an arm or a leg if she falls. Everyone says that she ruined her mother’s life when she was born. Not when they think Liv is in the room, of course, but she overhears all the same. In the kitchen of a less kind lord, a cook bearing a bastard child would have been more than cause enough for both of them to be out on the street. No, a child like Liv doesn’t have much hope. But when she accidentally unleashes a surge of wild magic, she takes her first step on a journey which will lead her from the kitchens of Castle Whitehill, to the cold palaces of the Eld, and beyond, to the graves of gods... What to Expect: - MC starts off very weak, with a lot disadvantages - not just physically weak, but also vulnerable in a socio-economic sense. She has talents, but it is going to take time to develop them. I want to give this process room to breathe, so I hope you enjoy long-term progression. - The MC begins the story as a child. As she grows up, she will have relationships that I intend to be appropriate for her stages of life, BUT THERE WILL BE NO SEXUAL RELATIONSHIPS UNTIL SHE IS AN ADULT. Expect eventual teenage drama progressing into more adult relationships. - There is action, but it is not constant action, and it will again be appropriate for the MCs development. As a child, she will be challenged by child things, and as she grows into power the scale of threats will increase.