Chaos Warlord: Reincarnated in Eldrich with the Devil System! - Chapter 296 293:

Son of the Senior Chancellor, Luo Wei, loved the wrong person in his past life. This mistake caused his entire family to be wiped out, and in the end, he was cast down as a pleasure slave, and died in the wilderness during the depths of winter.

Somehow, the heavens did not give up on him and gave him a second chance at life. He believed this rebirth was only meant for atonement, and not love. Yet, as he plotted his vengeance, Luo Wei quickly realized that passion would again be his fatal downfall.

The once emperor, the lover from his past life, his beloved in this life, and an opposing empire’s monarch who is doomed to love him, who is supposed to be good for whom?

And who is supposed to hurt whom? A hero chasing after a dream, an empire of a thousand years, a kingdom stretching across the known lands, all flashing before the eyes like a mirage. Is it worthwhile to trade a hundred years of my loneliness to give you a single lifetime of joy?

- Description from Novelupdates

In history, the most notorious Holy Knight! Corrupt Light! Holy Sinner! Blasphemer! The Irreverent! Wright has many well-known titles within the Church of the Holy Light.Angel: “The Goddess tells us to guard against fire, theft, and Wright!”Evil God: “Could you stop targeting me alone when you fleece us?”Evil Dragon: “He not only extorted my money but also abducted my precious daughter!”Devil: “Hell is still too kind and pure for Wright to handle!”Yet this man, whom the Goddess of Holy Light considers a thorn in her side, has become the world's most terrifyingly powerful Holy Knight!!Wright: “Do you believe in the light?”

Wrongly imprisoned for a crime she did not commit, Ye Qiao was freed from the iron gates that locked her away for seven years with nowhere to go, no one to see, and nothing to move on to following the passing of her husband, who she had never appreciated. The man was part of the Special Forces and had been killed during a mission.

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.