MTL - Perfect Secret Love: The Bad New Wife is a Little Sweet - v2 Chapter 1948 By my beauty

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.

Shen Yu's world is facing the apocalypse. With the help of his Gray Mist Space, he could do good things such as saving lives to gain more gray mist and use it to do everything he wants to do. And what's more, no one but him can survive in the Space. However, this time, two figures walk out of the Space, and when they spin around, Shen Yu is shocked, because the two figures are all him from different worlds.“Your world is facing an apocalypse too?”“Indeed.”

Ethan, a high school student that died alongside his bully transmigrated into another world.Ethan awakened in a parallel world, one where supernatural talents determined your worth, and the talentless serve as expendable cannon fodder.Born talentless in this new world, Ethan finds himself assigned as cannon fodder against the monster hordes that threaten humanity.But his death in the previous world seemed to have granted him a supreme Talent.Follow the story of Ethan as he awakens the strongest talent and strives to become the world's Strongest.

“O, Hero!” With that cliched line, Kazuya Souma found himself summoned to another world and his adventure–-did not begin. After he presents his plan to strengthen the country economically and militarily, the king cedes the throne to him and Souma finds himself saddled with ruling the nation! What’s more, he’s betrothed to the king’s daughter now…?! In order to get the country back on its feet, Souma calls the wise, the talented, and the gifted to his side. Five people gather before the newly crowned Souma. Just what are the many talents and abilities they possess…?! What path will his outlook as a realist take Souma and the people of his country down? A revolutionary transferred-to-another-world administrative fantasy series starts here!