System: My Doomsday Train - Chapter 2: No one wants to die, but there are always those who must.

Traveling through different worlds – this is unscientific!

Get cheats – it’s science!

…

This is a simple story. An ordinary person lives in a different world, farming and raising flowers, studying unscientific science in his free time.

until the end.

- 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.

The Chaos War, a time when even the gods fought for survival, was an unexpected and cataclysmic event. The reasons for its occurrence remain shrouded in mystery, and in the new era, all traces of the world before the war have been erased from existence.The universe, the immortal realm, and even the domain of the gods were all affected, and no one was spared from the aftermath of the conflict. The beings who lived before the war are now known as ancient gods, and their legends continue to captivate and inspire the people of the new era.Chen Tian, who was killed due to a treasure from the ancient era, finds himself reincarnated in a strange and unfamiliar place known as Earth.Unlike his previous life, the people here are only mortal and rely heavily on technology for their daily lives, and the concept of cultivation is unknown to them.Thinking that he would have an easy life in this new world, Chen Tian quickly realizes this world is far from simple.Join Chen Tian on his journey in discovering mysteries that will leave even gods shocked, and witness how he becomes a powerful cultivator, fighting against immortals and gods.

“I already have a child with another man.”

It was a lie made in order to refuse the proposal of the leader of the most feared mercenary company in the entire country. But his response was unexpected.

“It doesn’t matter who the child is. Just birth it.”

She couldn’t understand.

What could this man possibly want with the princess of a failing nation?