Jehu was king of Israel, the son of Jehoshaphat , and grandson of Nimshi. William F. Albright has dated his reign to 842 BC-815 BC, while E. R. Thiele offers the dates 841 BC-814 BC. The principal source for the events of his reign comes from 2 Kings 9-10.
The reign of Jehu's predecessor, Jehoram, was marked by the Battle of Ramoth-Gilead against the army of the Arameans, where Jehoram was wounded and afterwards returned to Jezreel to recover, and where Ahaziah, the king of Judah and his nephew, had also gone to attend on Jehoram (2 Kings 8:28f). The author of Kings describes, while the commanders of the army were assembled away from the eyes of the king, that the prophet Elisha sent one of his students to this meeting, where this student led Jehu away from his peers and anointed him king in an inner chamber, then immediately departed (2 Kings 9:5,6). 2 Kings is silent about the exact identity of this student. Jehu's companions, inquiring after the object of this mysterious visit, were told, and immediately, with enthusiasm, blew their trumpets and proclaimed him king (2 Kings 9:11-14).
With a chosen band, Jehu set forth with all speed to Jezreel, where he slew Jehoram with his own hand, shooting him through the heart with an arrow (9:24). The king of Judah, when trying to escape, was fatally wounded by one of Jehu's soldiers at Beth-gan. The author of Kings describes how Jehu entered the city without any resistance, and saw Jezebel, the mother of king Jehoram, presenting herself from a window in the palace, who received him with insolence; Jehu commanded the eunuchs of the royal palace to cast her down into the street; the fall was fatal, and her mangled body was devoured by the dogs (9:35-7).
However, Nadav Na'aman of Tel Aviv University has interpreted the evidence of archaeological excavations at the site of the city of Jezreel to show it had been taken by a successful siege, perhaps by the Aramean army of Hazael. Further, the author of the Dan Stele (found in 1993 and 1994 during archaeological excavations of the site of Laish) claimed to have slain both Ahaziah, and Jehoram; the most likely author of this monument is Hazael of the Arameans. Although the inscription is a contemporary witness of this period, kings of this period were inclined to boast and make exaggerated claims; it is not clear whether Jehu killed the two kings (as the Bible reports) or Hazael (as the Dan Stele reports). This suggests that this memorable scene was created (perhaps as a tradition) long after the principals of the coup had died.
Now master of Jezreel, Jehu wrote to the chief men in the capital Samaria, and commanded them to send to him by the morning the heads of all the royal princes of the kingdom. Accordingly, seventy heads were brought to him, which he had piled up in two heaps at his gate. Shortly afterwards, Jehu encountered the "brethren of Ahaziah" at "the shearing-house" (10:12-14), and slaughtered another forty-two people connected with the Omrides (10:14).
Jehu's revolt was rooted in more than his quest for power and the favor of the God of Israel. This account frequently invokes the slogan of "avenging the blood of Naboth" (9:21,25,26), whose vineyard Jehoram's father Ahab had taken by force (1 Kings 21:4); this fact suggests that perhaps the burden of making the northern kingdom a regional power had grown too heavy for its citizens, and Jehoram's defeat at Ramoth-Gilead gave them an opportunity to throw this burden off.
Following Jehu's slaughter of the Omrides, he met Jehonadab the Rechabite, whom he took into his chariot, and they entered the capital together. This adds support to the inference that, at least at the beginning of his reign, Jehu was supported by the pro-God of Israel faction. Once in control of Samaria, he summoned all of the worshippers of Baal to the capital, slew them (2 Kings 10:19-25), and destroyed the temple of that deity (10:27).
Beyond his bloody coup d'etat, and his tolerance for the golden calves at Dan and Bethel (which drew the disdain of the author of Kings), little is known of the events of Jehu's reign. He was hard pressed by the predations of Hazael, king of the Arameans, who is said to have defeated his army "throughout all of the territories of Israel" beyond the Jordan river, in the lands of Gilead, Gad, Reuben, and Manasseh (10:32f). This would explain why Jehu is offering tribute to Shalmaneser III on his Black Obelisk (where his name appears as mIa-ú-a mar mHu-um-ri-i or "Jehu son of Omri"); Jehu was encouraging the enemy of the Arameans into being his friend.