Because I've Been Reincarnated as the Piggy Duke, This Time I Will Say I Like You - Chapter 115: Free Commonwealth: Dungeon City Universe

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.

At twenty, she had a child in secret.At twenty-two, she was discreetly married into a wealthy family.Qin Mu lost her mother at the age of seven and was sent abroad by her unscrupulous father when she was only eight. Little did she expect her future to be so bright, she decided to climb up on Mu General's shoulders with great strides.Mu Yichen went from being Rongcheng's top heartthrob to its youngest tycoon—arrogant and wise, unfathomable, yet he somehow fell into the hands of a little lass.——About marriage.“Mu Yichen, we are just—friends!”“That can't be the reason you reject me!”Qin Mu was scared stiff, as Mu General rudely carried her off to the marriage registration office, to sign, to stamp, to get the certificate!——Hidden marriage for too long.“If you say our daughter is adopted from the orphanage, I won't argue with you, but when will you make me public?” In broad daylight, Mu General pinned Mrs. Mu against the corner wall, threatening her with a devilish charm.“Depends on your performance!” Mrs. Mu smirked, and the next moment, she counterattacked Mu General.“Quick, cover your eyes!” Mu Baby, who had been ignored on the side, immediately covered her eyes.

Gu Nianzhi had no idea how to get the aloof and handsome Major General to fall in love with her.

His eyes were dark and serious. “…Seduce me. If you can do it, I’m yours.”

Gu Nianzhi: “!!!”

- Description from Novelupdates

A piece of divorce paper sent Xia Xinghe into a state of destitution. However, a car accident later, she transformed into a professional hacker with more money than she could ever spend. All those that have belittled, bullied and laughed at me, please line up, I’ll show you what the meaning of face-slapping is! Wait, wait, wait. That guy over there, the ex-husband that I no longer have any relations with, don’t cut in line. What, you want to help me face-slap these people? “Not only that I will help you face-slap myself!” The wickedly handsome man with billions of dollar in estate raised his own palm to slap his own face without reservation!

- Description from Novelupdates