Amaziah was the son and successor of Joash and eighth king of Judah. He was twenty five years old when he ascended the throne and once his kingdom was firmly in his control, he executed the murderers of his father.
He built up his army, recruiting 100,000 mercenary soldiers to fight for him. On the advice of a prophet, however, telling him that with God on his side, he didn't need extra forces, he discharged them, much to their annoyance. He then proceeded to go to war with the Edomites, utterly routing them. Flush with his success he challenged Jehoash, son of Jehu and king of Israel to battle. Jehoash warned him not to be adventurous.
But Jehoash king of Israel replied to Amaziah king of Judah: "A thistle in Lebanon sent a message to a cedar in Lebanon, 'Give your daughter to my son in marriage.' Then a wild beast in Lebanon came along and trampled the thistle underfoot. You have indeed defeated Edom and now you are arrogant. Glory in your victory, but stay at home! Why ask for trouble and cause your own downfall and that of Judah also?"
(2 Kings 14: 9-10)
When Amaziah refused to listen, Jehoash attacked. Having lost favor with God for resorting to worshipping some of the idols he had captured from the Edomites, Judah suffered a humiliating defeat as Jehoash broke down a large part of the wall of Jerusalem and took all the god and silver out of the temple. This probably brought about a conspiracy that cost him his life. He was slain at Lachish where he had fled having reigned for twenty nine years.
He was succeeded by his son Azariah.