The reign of King Jeroboam II was a period of relative weakness in Assyria, where they just endured several epidemics and internal political turmoil. A young Assyrian general named Tiglath-Pilasser III (called Pul in 2 Kings) seized power in the midst of this turmoil, and began reasserting Assyria's domination. From that point until the final destruction of the Northern Kingdom in 722 BC, the kings of Israel continued to lose power, yielding to the great empire from the north.
King Menahem of Israel paid Tiglath-Pilasser three million shekels of silver to keep him from attacking the nation around 743 BC (2 Kings 15:19). Ten years later, however, King Pekah of Israel joined forces with Syria and attacked Judah in the south. King Ahaz of Judah called on Tiglath-Pilasser to help. The Assyrian army needed little to entice them to wage a campaign against its southern neighbors. In 732 BC they destroyed the Syrian capital, Damascus, invaded large sections of northern Israel, and carried off the residents to captivity (2 Kings 15:29). Hoshea, the next king of Israel was forced to pay tribute to Assyria.
In 722, Tiglath-Pilasser's son, Shalmaneser V, discovered that Hoshea was plotting with Egypt to rebel against him. So he destroyed the capital of Israel, Samaria, and carried away all the people of Israel into captivity.