You're My Mate (BL) - Chapter 180

Tian Man Continent is a world of martial arts. A young boy named “Su Yi” led countless yao (monsters or demons) and overrode countless families who had thousands of years of history. He rose abruptly in the world as the brightest star in the sky. He married beauties and walked towards the peak of of the world, and finally ascended onto the thrones of the ancient gods!

- Description from novelupdates

After traversing through time, Li Xuan was delighted to have become the second son of Earl Chengyi's mansion, as well as a proud warrior of Liudao Fumo. However, just ten days into his privileged life, he faced fierce female supervisors, terrifying ghost-girls, and spiteful demonesses one after another.Amidst this whirlpool of challenges, Li Xuan claimed he didn't feel a bit panicked. A few years later, standing above the Yangtze River, he swung his sword, and with that, thousands of miles of landscapes were instantly frozen.Where will the demoness escape to? Take my sword!

The day of marriage. Lifting the sedan chair to the door, he lightly lifted the sedan curtain, but he saw no newcomer, only a piece of paper pressed under a stone.

Looking at her flamboyant font, his thousand-year-old pupils faintly spurted out a few flames. good very good. On his perfect and impeccable face, there was a faint smile, not angry but smiling.

However, no one saw the hidden chill in that smile. That woman dared to run away from marriage, he would let her know the consequences of doing so.

- 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.