10 O you that are exalted and lifted up, let not the vaunting of your heart mislead you, nor say, I will go up against the rich land and against the powerful beast. For that beast will not be slain by the ram seeing that its horns are broken. For the he-goat broke the horns of the ram. Now the he-goat has become the mighty beast. For when the children of Japhet held the kingdom, then they slew Darius, the king of Persia. Now the fourth beast has swallowed up the third.
And this third consists of the children of Japhet, and the fourth consists of the children of Shem, for they are the children of Esau. Because, when Daniel saw the vision of the four beasts, he saw first the children of Ham, the seed of Nimrod, which the Babylonians are; and secondly, the Persians and Medes, who are the children of Japhet; and thirdly, the Greeks, the brethren of the Medes; and fourthly, the children of Shem, which the children of Esau are. For a confederacy was formed between the children of Japhet and the children of Shem.
Then the government was taken away from the children of Japhet, the younger, and was given to Shem, the elder; and to this day it continues, and will continue for ever. But when the time of the consummation of the dominion of the children of Shem shall have come, the Ruler, who came forth from the children of Judah, shall receive the kingdom, when He shall come in His second Advent.
Source: Demonstrations (New Advent)