In פרק י the Jews sinned once again, and Hashem wanted them to realize that if they continued to sin they would be brought into exile. Since they did not change their ways Hashem sent Assyria to attack them and put them in exile. But Hashem wanted to make sure that the Jews knew that the Assyrian's attack was because they were sinning and that Hashem sent them to the Jews. But he also needed to make sure that the Assyrians knew that it wasn't their own strength that put them to war. The Assyrians are being arrogant by thinking that all the power came from them. 
We need to remember that everything in our lives is from Hashem whether it is good or bad. If it is something good we have to remember that everything comes from Hashem. If you get a good grade on a test, you should remember that Hashem had a part in making it happen. If it is something bad we have to remember that we were given it for a reason, and we need to try to do better because of it. Also if something very unfortunate happens we have to remember that Hashem did it for some sort of reason, and we just cannot see the full story. Like the event that just happened in Boston. This horrible tragedy was taken place for some sort of reason by G-d, but we will never understand completely because we cannot see the whole picture.