Assyria was named after Asshur, the second son of Shem, who was the oldest son of Noah. Asshur means straight, or going straight, as in going ones own way, which comes to mean going astray.
Assyria was the empire located north of Israel.
Assyria was one of the first empires of human history.
Assyria eventually conquered Syria, and then the northern kingdom of Israel, and then the southern kingdom, called Judah.
Eventually Assyria would be conquered by the Babylonians, and replaced by the Babylonian Empire.
Assyria was a powerful empire, as noted here, as they struck with a rod, referring to their weaponry or military might.
However, in contrast, God strikes with His voice, setting the voice of God against the rod of Assyria.
Humanity has innumerable plans, plans beyond counting, and none of them work.
God has one plan, which has existed since eternity past, and it has never changed, but has worked perfectly and always will.
Humanity boasts of many weapons, from fists to rocks and clubs, to arrows and guns, and missiles and bombs, and on and on.
God has one weapon, namely truth, which He exercises with the power of His voice.
No matter what weapons, or power, or resources that humanity, or a person has at his disposal, the voice of God is far superior and can inflict complete and total destruction without ever missing, and is far more terrifying than anything that man has used or invented.
It is far better to be on the side of God, than to be opposite of God.
And to be on Gods side, all one has to do is comply with the mandates that are spelled out in the Bible, namely faith in Christ, and pursuing ones spiritual life, while in fellowship, by means of a daily Bible study.