I'm the Owner of the Pokémon Day Care In the World of Pokémon - Chapter 1339: Unexpected Opportunity

He was an addict, a loser, a despicable human being.

Ace had always harbored feelings for his childhood friend, only to have his heart shattered when he learned she was secretly in love with Duke. The betrayal left him disheartened, but nothing could have prepared him for what came next.That night, instead of waking up to another ordinary day, he opened his eyes in a completely different world—inside another man's body. Worse still, the first thing he heard upon waking was yet another rejection.Thrown into an unfamiliar land with a past he doesn't remember and a future he never planned for, Ace faces a choice: chase after love once more or embrace a new passion—one that comes in the form of an unexpected farming system. As he cultivates spirit crops and reaps rewards beyond imagination, he begins to wonder: perhaps love isn't found in a person, but in the soil, the growth, and the endless possibilities of the land.Will Ace sow the seeds of a new destiny, or will the echoes of rejection root him in the past?

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.

Kenichi Yamada was a 35-year-old salaryman. As a hardcore game enthusiast, he was saddened by the modern trend towards casual games.

So, when a site claimed to be “for people who like to do things the hard way,” he just couldn’t resist. Thus, he was reincarnated into another world as Allen, playing on Hell Mode.

This is fantasy light novel about Allen’s journey as a summoner.

Reincarnated as a serf, he starts from nothing.

His journey begins with absolutely no knowledge of the world around him, just like those games he played 10, 20 years ago.