Time-Traveling Crown Prince

Lysander is a man from the present day who wakes up in ancient times as the crown prince of the Great Zhou. He uses what he knows to pull the dynasty out of its troubles. The third prince, Thaddeus, works together with the emperor's consort Persephone to claim the credit for that work, and they have Lysander killed. Lysander opens his eyes on the night before the coup. This time he finds out what the jade amulet he carries does: it summons modern technology. He takes power by force instead, settling debts with everyone who wronged him. The barbarian tribes threaten the border and he handles them without much difficulty. Trouble then breaks out at the palace and he returns to put down the rebellion and take the throne, after which he turns modern weapons on the barbarians.