The Savior is just a 3-Year-Old - Chapter 1536

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.

When a glorious old civilization was toppled overnight, a strange purple moon rose and thus began the Purple Moon Era.

His Royal Highness the King of Han, who was afraid of the dark and ghosts and loved to cry, has always been the good baby of the princess.
Until one day, His Royal Highness the King of Han found a book in the bookstore…
Picture book?
Content tags:
Search keyword: Protagonist: King of Han, Princess of Han

- Description from novelbuddy

For three years, Finn Taylor is utterly humiliated. He has endured everything from physical beatings to verbal abuse. For three long years, he has gone by only one identity—the useless matrilocal son-in-law of the Larson family. But this life as he knows it is about to be turned upside-down as he reclaims his position as the head of Peregrine Hall.