God causes the Assyrians to waste away because of their wicked pride fullness (Isaiah 10:16–19 ESV).  What characterizes an arrogant, prideful heart?  I did it, I am strong & capable, I am smart & wise, I understand, I make things happen, I overcome, I am unopposed, I have the right perspective.  When we walk in pride we believe that our strength and savvy is what makes things happen.  See the emphasis on “I?”  ““By the strength of my hand I have done it, and by my wisdom, for I have understanding; I remove the boundaries of peoples, and plunder their treasures; like a bull I bring down those who sit on thrones. My hand has found like a nest the wealth of the peoples; and as one gathers eggs that have been forsaken, so I have gathered all the earth; and there was none that moved a wing or opened the mouth or chirped.”” (Isaiah 10:13–14 ESV)
There is coming a day when God will judge the Assyrians for their wickedness.  God (and Isaiah) seem to be OK with using one wicked people (Assyria) to judge another wicked people (Israel) and then turning around and judging the first wicked group (Assyria).  Only in the providential control and guidance of God does this make sense:  “Therefore thus says the Lord GOD of hosts: “O my people, who dwell in Zion, be not afraid of the Assyrians when they strike with the rod and lift up their staff against you as the Egyptians did. For in a very little while my fury will come to an end, and my anger will be directed to their destruction. And the LORD of hosts will wield against them a whip, as when he struck Midian at the rock of Oreb. And his staff will be over the sea, and he will lift it as he did in Egypt. And in that day his burden will depart from your shoulder, and his yoke from your neck; and the yoke will be broken because of the fat.”” (Isaiah 10:24–27 ESV)