A Great Light
Isaiah 9:2 describes the contrast between the people walking in darkness and the light that is shined on them. Ludlow suggests that there are three possible interpretations for this verse.
The first one is that the darkness represents Assyria and the light represents "the king who protects his people from Assyria" (153). Since Hezekiah is the victorious king who later defeats the Assyrians, he is the "light."
The second interpretation is that the darkness represents Israel's wickedness and the light is her recognition of those sins and her attempt to change. Both Isaiah and Hezekiah helped reform the Israelites after their captivity.
The third is the most common Christian interpretation. The darkness represents "a period of wickedness and apostasy" and the light of Christ dispels the darkness. Matthew 4:12-16 explicitly refers to Christ as the light.
Isaiah 9:3-5 seems to fit with each of the above interpretations. Viewed through the lens of each interpretation, we can see how Israel defeats Assyria; how Israel overcomes her wickedness; and how Christ defeats sin and death.
"For unto us a child is born"
I really love the words in Isaiah 9:6-7. Every time I read this passage, I think of Handel's Messiah. One of the most ingrained memories I have as a young man is that of going to The Messiah at Christmas time with my mom. She is the one who first told me how Handel locked himself in a room writing this masterpiece. When it was finished he exclaimed, "I did think I did see all Heaven before me, and the great God Himself." A simple search of the Internet will register a handful of versions of this story, but none seem to have a source. The common element is that Handel feverishly wrote The Messiah in 24 days and when he finished the Hallelujah chorus, he was in tears and uttered those words (http://www.theviolincase.com/Newsletter/Dec04.shtml). Whether the story be true or not, the feelings and awe that this work inspires in me shakes me to the core and brings me to tears.
Four Warnings to Israel
Isaiah gives four major warnings to the northern kingdom of Israel. With each warning he tells them, "For all this his anger is not turned away, but his hand is stretched out still." In other words, depending on how the people react, His hand may be outstretched to mercifully help if they repent or it is held out to smite them down in their wickedness.
In Isaiah 9:10, the people say that even if they are destroyed by the Lord, they will take the fallen bricks and build an even better city. In this their pride is manifest.
Since the people did not turn to the Lord, nor sought him, He will take away their leaders. Perhaps the leaders tried to warn the people and the people did not heed them, therefore the Lord took their leaders away. Or perhaps the leaders did not properly lead the people and therefore the Lord took them away.
Isaiah 9:18-21 we read how selfish the people are. "No man shall spare his brother." Everyone is so selfish that no one will help his brother in need.
The needy and poor and the widows and fatherless do not receive any justice. The people will not succor those in need. Therefore the Lord will not succor His people in the day of their need. "Without me they shall bow down under the prisoners, and they shall fall under the slain" (Isaiah 10:4).
Assyria: A Tool in the Lord's Hands
We learn from Isaiah that Assyria was a tool in the Lord's hand. But instead of heeding the Lord, Assyria seeks to not only take what the Lord has allowed, but to take more. "It is in his heart to destroy and cut off nations not a few" (Isaiah 10:7). For this pride the Lord will "punish the fruit of the stout heart of the king of Assyria, and the glory of his high looks" (Isaiah 10:12).
The Lord rhetorically asks, "shall the axe boast itself against him that heweth therewith?" (Isaiah 10:15). We can all be tools in the Lord's hands. But we must never boast of our own accord. In all we do, we must recognize the Lord's hand. I am reminded of something I learned in my humanities class at BYU. JS Bach often signed his compositions with SDG. SDG is Soli Deo Gloria which is Latin meaning "for the Glory of God." I think that if more of us held the perspective that our lives should bring glory to God, then our actions would be more in tune with His will and will would truly be instruments in the Lord's hands.
As Ludlow points out, Assyria was eventually annihilated by the Babylonians and Persians beginning with the sack of Nineveh in 612 BC.
The Hope of the Remnant
Despite the Assyria conquest, Israel will return. The Lord gives the people hope by telling them that a remnant will return. This remnant will not only return to their lands, but they will return to the Lord.
The Lord also promises that the Assyrian army will come close to Jerusalem, but will not conquer her (Isaiah 10:28-32). The Lord will cut down the Assyrians before they can invade. This passage also foretells of the time before the 2nd Coming of the Lord (see Zechariah 14:2; Revelation 11:1-13; and JST Matthew 24).