Toaru Majutsu no Index: New Testament - Volume 4, Main.12

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.

“Let me tell you something honey, Revenge is the best dish served cold.’’****To her, betrayal was the most excruciating pain in the world—the kind that pierced her soul.The people she had loved with her entire heart had not only failed her, but ruthlessly deceived her.“How could you?” she had once cried, her voice shaking as she stared at the man she had chased like a madwoman. But he had already cheated on her—expecting a child with the very woman she despised with every fiber of her being.Her so-called “family ” was no better. The relatives she thought she could trust? They only wanted the inheritance meant for her and her little brother.The people who once smiled sweetly and flattered her? They were nowhere to be found when her glamorous and envious life crumbled to nothing.“I thought you all cared about me...” she whispered bitterly, watching as one by one, they all turned their backs on her when she needed them the most.In that devastating moment, everything became painfully clear. The bubble she had lived in popped and she finally saw their true faces.But....it was too late.Everything she had was gone, slipping through her fingers like sand in the wind.Except for him.Her former fiancé, the one man she had tried to ruin with every scheme she had planned, remained by her side until the end. He stood by her, even as she took her final breath.She had accepted her tragic fate—until something phenomenal happened. She woke up once again.Back to the past.Where nothing had happened yet.

While most cultivators were scratching their heads as they pondered how to advance to the next realm, Li Lang was busy systematically studying the mechanics of cultivation.Scientist Langley Seiker has always dreamed about immortality. Reincarnating into a world of cultivation, it is no longer a dream except for the fact that he has no talent. However, through a chance encounter, he gains access to his familiar laboratory that will allow him to study the wonders of cultivation.Not even the heavens will know what fate has in store for Langley as he systematically unravels not only how to cultivate, but also various crafts such as refining pills and inscribing talismans. Preparation is key to surviving in the merciless world of cultivation, especially for those with no talent.Expectations:- Detailed study of each stage of cultivation and crafting- Not technology vs cultivation, scientific method will be used to study cultivation- No harem- Slow burn progression. MC won’t be skipping through cultivation ranks at record speed- Weak to Strong- Sect Building (Much later in the story)