One Piece: From the Rocks Era to King of the World - Chapter 408 - : Some are happy, some are sad

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.

A sudden and inexplicable transformation has caused the entire global population to be reborn in the struggle for survival on the Continent of Overlord.Each person reborn on the Continent of Overlord is randomly reincarnated as a species - some come to life as weeds only to be trampled to death by passing monsters, while others emerge as dominant beings like dragons, naturally ruling the skies...The Dark Creatures invade this other world with reckless abandon, instilling fear and dread across the realm.Reborn the night before the transition to the Continent of Overlord, Charles activates the Zerg Clan System, becoming the Overlord of the Zerg Clan!While others are still grappling with the darkness of the Continent of Overlord, Charles has already constructed a fortress spanning the entirety of Zerg Clan territory and casually wipes out countless Dark Creatures with a burger in one hand and a cola in the other....【Ding! A female has been detected as 100% loyal to the Host. The Zerg Clan System is awakening!】Zerg Queen Catherine: “Master, I've just bought a very thin nightgown. Would you like to experience it personally?”Snake Queen Medusa: “Master, I've already trained these troops for you. When will you train with me?”Snake Emperor Yggdrasil: “Cursed Medusa, don't think of stealing my master!”Elf Goddess Eve: “Silence, all of you! I'm the only true queen, you all are just concubines.”While everyone else struggles to survive and defend against the Dark Creatures...Only Charles raises the divine flame, waging war across the stars!

She is a waste daughter from the Su family that couldn’t cultivate. On the day before her wedding, the Third Prince breaks off their engagement in the street. Her own sister replaces her in the marriage to the Third Prince. She became the center of gossiping in the city. In her resentment, she hits herself on the Su Family’s gate, only to become the object of other people’s ghost marriage.