Demonic Dragon: Harem System - Chapter 795: I am the strongest.

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.

Kōdo Ikusei Senior High School, a leading prestigious school with state-of-the-art facilities where nearly 100% of students go on to university or find employment. The students there have the freedom to wear any hairstyle and bring any personal effects they desire. Kōdo Ikusei is a paradise-like school, but the truth is that only the most superior of students receive favorable treatment.The protagonist Kiyotaka Ayanokōji is a student of D-class, which is where the school dumps its “inferior” students in order to ridicule them. For a certain reason, Kiyotaka was careless on his entrance examination, and was put in D-class. After meeting Suzune Horikita and Kikyō Kushida, two other students in his class, Kiyotaka’s situation begins to change.Note:- Even though Volume 0 is the prequel of this series, it is advised to read till Year 2 Volume 8 beforehand to avoid getting spoiled (which is precisely the reason why it was released after Y2 V8).Anime:-Season 1: Volume 1 to 3 + Volume 4.5Season 2: Volume 4 to 7 + Volume 7.5Season 3: Volume 8 to 11 + Volume 11.5

[Congratulations, you have earned +9 coins. You have repaid 999,999,999 / 1,000,000,000 Coins. You need 1 more coin to repay your debt.]“You’ve got to be kidding me.”______After living a hundred lives, Lucian finally managed to repay his debt to the system. World after world, he fought, bled, and struggled—all for the freedom he had foolishly given up the day he begged the system to save his life.At last, he had done it. 999,999,990 coins. Just one more mission, one last world, and he would finally be free...Or so he thought.But this was no joke. The system had screwed him over one final time.Still, there was hope. With only a single coin left to repay, the system could no longer play its tricks. Freedom was just within his grasp—if he could survive this last world.All Lucian had to do was reach the end. Simple, right?Except this time, the world itself seemed determined to destroy him.

19 year old son of Earth's Destiny Hero, Shiro Moji, Ryder Dawn is tasked with a fate only he can complete as one of three Destiny Children. As a sophomore of a top university in Texas, Trinity Valley University, Ryder only wants to live a normal life without the stress of being the hero Earth needs.Once Ryder is ready to confront his fate, his mentor and guardian, Charlotte White, takes him under her wing as the The Ace in her organization, Sanctuary Agency.Their main goal as the agency is to stop the Syndicates once and for all, bringing back the peace Shiro and Karma fought hard to bring to Earth.