After Giving Birth, All My Beast Ex-Husbands Suddenly Want Me Back - Chapter 42: Bland

You take up a student career.

Student career upgrade to lv.7

Acquired skills: primary school knowledge, junior high school knowledge, high school knowledge.

You take the college entrance examination,

You got a perfect score.

Your basic occupation has been upgraded to lv.9, and the job transfer system has been activated.

You change jobs to become a scientist, you gain R&D skills

You use research and development skills to get space fortress construction technology

You use R&D skills to gain starship technology.

You are invincible.

- Description from novelbuddy

The countries of Mephius and Garbera have been waging a war for ten years and are trying to put an end to this long fight through a political marriage between the two royal families. Orba, who was driven from his home because of the war and was forced to become a gladiator, looks exactly like the crown prince of Mephius, and it has been decided he will be substituting him during the wedding ceremony. On the other hand, Vileena, the princess of Garbera, has secretly decided to ensnare the crown prince for her own country’s interests.

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.

After the nuclear war, the world was controlled by twenty mega-corporations that established a global government. Governed by AI, it judged everything.Gao Xin, who had only wished to live a peaceful life, inexplicably became a scapegoat for the elite and, unable to pay the imprisonment fee, was sentenced to ten years of exile on Crime Prison Island!On this island, there were no laws, no constraints, the only order being the numerous game arenas set up by the officials.The criminals could only participate like racehorses for the entertainment of the elite.Yet, on this prison island filled with Radiation, cyborgs, and many powerful villains, Gao Xin had no strength, no talent, and no background—like a sheep thrown into a crocodile pool, no different from being on death row.How could an ordinary person like him survive under the oppression of the strong, the geniuses, and the wicked? Unless in this world, there was a path, a path that allowed even the weakest to continuously break their shackles.