The Chronicles of Van Deloney - Chapter 29: DEAD LIVING IN THE MEMORIES

Lu Wu, an aimless video game developer, had been feeling perturbed ever since he found out he was the direct descendant of a king from the underworld. Other than the title, His Excellency, his ancestor hadn’t passed down anything else to him. On top of that, all of his ancestor’s subordinates had rebelled against him and completely usurped his inherited territory.

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.

"What you do in life, Echoes in Eternity."

The System, who goes by the code name, Thirteen, defied the System God in order to give his previous Hosts’ the chance to change their Fates.

Unfortunately, he was killed by his Father, the System God, and was sent to the world of Pangea to struggle like the Cannon Fodders that he fought so hard to protect.

Armed with his knowledge as a System, Thirteen vowed to change not only his Fate, but the Fate of others whose destinies were tied up with him.

In a world torn by power and corruption, a fallen System will bring out a symphony of change, or lead it to its destruction.