Qin dynasty
Note: King Zhaoxiang of Qin (秦昭襄王) had already been ruling Qin for 51 years when Qin annihilated the Zhou dynasty; however the other six warring states were still independent regimes. Some Chinese historiographers thus used the next year (the 52nd year of King Zhaoxiang of Qin) as the official succession from the Zhou dynasty.
Qin Shi Huang
In 246 BC, when King Zhuangxiang died after a short reign of just three years, he was succeeded on the throne by his 13-year-old son. At the time, Zhao Zheng was still young, so Lü Buwei acted as the regent prime minister of the State of Qin, which was still waging war against the other six states. Nine years later, in 235 BC, Zhao Zheng assumed full power after Lü Buwei was banished for his involvement in a scandal with Queen Dowager Zhao.