Because the northern tribes do not want to travel all the way to Jerusalem to worship, they build two new shrines in Bethel and Dan. The South views this as disrespectful to the Lord; however, from the archaeological evidence, it is clear that they built alternate shrines as well (Beer-Sheeva and Arad Temple).
After the division of the United Kingdom, there is a numerous amount of infighting between Judah and Israel. For instance, Baasha (King of Israel) attacks Asa (King of Judah) around 875 BCE, causing Asa to seek the help of Ben-Hadad of Syria by paying him tribute form the Temple. Later, another king of Israel, Jehu, lets his kingdom become a vassal of the Assyrian Empire (an inscription was found depicting the tribute from Jehu to Shalmaneser III) in 841 BCE.
The Assyrian Menace began around the 8th c. BCE along the fertile crescent. From Tiglath-Pileser III (745 - 727 BCE) to Shalmaneser V (727 - 722 BCE), Assyria becomes a force to be reckoned with as they conquer and exile those in Israel. Meanwhile, Israel (before their exile) and Judah constantly try to play Assyria and Egypt against each other in hopes that that conflict will preoccupy both powers and keep them at bay.
Then, in 721 BCE, the Northern Kingdom falls (Samaria is down), and thus begins "ethnic cleansing" in the form of deportation, rape, and murder. Sargon II contributes to the deportation started by Shalmaneser V. Some believe that the fall of the Northern Kingdom was due to the Hand of God--that because the Northern tribes seceded, they were punished. Important to note however, is that with the fall of Israel comes the rise of Judah, as many exiles of Israel flee to Jerusalem for comfort.
The Assyrians were known for their ruthless tactics of conquest, as Shalmaneser III brags about his murder of many innocent lives. Common during such a time period were public displays of murder used in an effort to spread fear.
As the Assyrians are establishing their stronghold over the Canaan lands, Jerusalem is rapidly growing due to the downfall of Israel. There is increasing industry and a thriving global economy, along with an increasing population. Because Jerusalem becomes stronger, it also becomes a threat to the Assyrians. Proof that such was the case can be found in the archaeological evidence of King Hezekiah's preparations for siege. The construction of the "Broad Wall" and "Hezekiah's Tunnel" are evidence to the fact that Hezekiah was fortifying Jerusalem.