Isekai Kaeri no Ossan wa, Fusei Sukiru de Fathercon Musume-tachi o Tororori ni - Chapter 56: Expanding Defense Perimeter

“Even death can't stop me from reaching the top.”Alex clawed his way to the top through sheer hard work and ruthlessness, only to be betrayed by someone within his own group.Although he managed to kill the traitor, he lost his life in the process.But just when Alex thought it was the end, fate had other plans for him.Reincarnated into the world of a novel his girlfriend used to read, he was given a second chance at life.His goal remains the same, but this time, he awakened a mysterious system and surrounded by a harem of alluring beauties.Follow Alex journey through this vast new world as he uncovers the truth behind his reincarnation and the otherworldly goddess who made it all possible.

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

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.

Lin Ke traversed to this world and, with the help of a system, utilized modern knowledge to farm and develop, claiming kingship and dominance.This is a world of professionals, a world of swords and magic, a world of bloodline inheritance, and a world of countless racial conflicts!One day, Lin Ke rode a bicycle with training wheels past the army, facing an endless enemy ahead.[Shield Warrior], [Arsonist], [Tree Shepherdess], [Wind Whisperer], [Thunder Sword Maiden], [Eternal Freeze Knight], [Voodoo Warlock]...Looking at the diverse group of followers behind him—tall, short, plump, thin, old, weak, sick, and disabled—Lin Ke laughed and raised his arm to call out: “[Workers]! Delivery [Knights]! [Scientists]! [Doctors]... Raise the flag of Azanen and charge with me!”Thus, amidst the eerie cries and howls of his followers, the history of the boundless planes was forever changed.