Genesis 10:11

From that land went forth Nimrod, and reigned in Athur, because he would not be in the counsel of a divided generation. And he left those four cities; and the Lord thereupon gave him a place; and he builded four other cities, Nineveh and Pelatiath, Kartha and Parioth.

OUT OF THAT LAND — when Nimrod reigned over it — WENT FORTH ASSHUR, meaning he went forth to Asshur for Asshur was one of the sons of Shem. This usage is similar to that found in the verses: And it shall go forth Hazar-addar, and pass along to Azmon, [which means that it shall go forth to Hazzar-addar]; And Og the king of Bashan came out against us Edrei, [which means at Edrei]; And he shall return his own land with great substance, [which means that he shall return to his own land]; and many other similar verses. This is why the land of Assyria is called the land of Nimrod, just as it is said, And they shall waste the land of Assyria with the sword, and the land of Nimrod with the keen-edge sword, alluding to Nineveh, and the city of Rehoboth, and Calah. Scripture tells yet more about Nimrod’s prowess — i.e., that he was a mighty hunter, prevailing also over the animals and ensnaring them. Scripture said, Before the Eternal, to suggest wonderment for there was no one under the heaven like him in strength. Similarly, And the earth was corrupt before G-d, means that everything before Him on the earth was corrupt. This is like the verse, That soul shall be cut off from before Me, since every place is “before Him.”

מן הארץ ההיא יצא אשור, he emigrated from there because he disagreed with Nimrod politically, i.e. he opposed the building of the Tower (fearing that G’d would punish the people including his children who were associating themselves with rebellious project)

ויבן את נינוה, because he had distanced himself from the plans undertaken by the four countries under the rule of Nimrod in the land of Shinor, G’d rewarded him to let him build the four cities mentioned here. This is an instance of אל פניו ישלם לו, of G’d recompensing someone for a good deed “to his face,” i.e. so that he can realise that this is what G’d has done for him. (Deuteronomy 7,10)

מן הארץ, from the land of Ashur he went forth in the direction of Assyria. The Torah fails to tell us if Ashur belonged to the descendants of Cham or of Shem. In verse 22 we are told that Eylam and Ashur were sons of Shem, so that it is unlikely that here we speak of a descendant of Shem, the subject matter being the descendants of Cham, i.e. Kush. However, seeing the Torah did not mention another Ashur, it is most probable that he was a descendant of Shem. Perhaps he had made his home for a while in the land of Shinor, i.e. regions populated by the descendants of Cham, so that the words מן הארץ ההיא יצא אשור gain added significance, seeing that this was the first example of someone migrating from one region to another. Perhaps Ashur had even overcome Nimrod or his successor in the land of Shinor and founded a rival kingdom in Nineveh. His kingdom, as distinct from its capital, may have been named after its founder, Ashur. We definitely have evidence that the King of Ashur ruled over Babylon and its surrounding region. The various descendants of Cham were expelled from that entire region, being supplanted by the Chaldeans, כשדים, in the time of Avraham. These people were descended from Shem, [else how could Avraham have been at home there? Ed.]
This whole story is only meant to remind us that the entire universe belongs to G’d, no matter how great the conquerors on earth, (Psalms 24,1 and Samuel I 2,9) and if He decides to take away a country from its ruler and to substitute new inhabitants and rulers, He will do so at will. This is what the prophet Jeremiah 27,5 spoke about when he said ונתתיה לאשר ישר בעיני “I will give it (the land) to whoever is right in My eyes.” Ownership of a part of the earth is totally dependent on the deeds or misdeeds of the people living on that land. (Deuteronomy, 32,4). We are not sure if the word Ashur refers only to a city or to an entire kingdom. The verses (25,18 in Genesis, or Kings II 15,19), speaking of מלך אשור, or Kings II 19,11, speaking of מלכי אשור, do not give clear guidance on that point. According to Yuma 10, in the name of Rabbi Yossi, Ashur is equivalent to סלוק, (Silikia? in Iraq, on the banks of the Tigris)