Dan 11:1-3

THE KING WHO STIRRED UP GREECE
Here, the Angel begins the long explanation of Daniel’s vision. This is the longest prophecy in the Bible.

In verse 1-3, the Angel described the Persian King who stirred up the third beast. King Xerses I, flaunted his wealth before Greece, and stirred them up. Just as King Hezekiah flaunted his wealth before Babylon, and stirred up the first beast.

In verse 4-30, the Angel will describe how the fourth beast was stirred up.
1 “As for me, in the first year of Darius the Mede, I stood up to confirm and strengthen him.
Dan 11:1
In the first year of Darius, I stood up to confirm and strengthen him – here the Angel introduces the phrase “stood up” AMAD, that will be repeated a number of times in this Chapter, to describe the Kings who “stand,” and ultimately, Michael, WHO IS LIKE God, who “stands” in the LORD’s Day, in Dan 12:1. The Angel, is saying that he fought on behalf of Darius, to allow him to stand, before Cyrus took power.
2 Now will I show you the truth. Behold, there shall stand up yet three kings in Persia; and the fourth shall be far richer than they all: and when he has grown strong through his riches, he shall stir up all the realm of Greece. 
Dan 11:2
now I tell you the truth – this will begin the “Book of truth,” introduced in Dan 10:21.

there shall stand up yet three kings in Persia and the fourth shall be far richer than them all– the fourth, after Cyrus the Great, was King Ahasuerus (Xerses I, 485–465 BC). In Esth 1:4 we are told that he displayed all the riches of his glory and majesty for 180 days. His palace was twice the size of his father’s, and his taste in architecture was similar, but on a gigantic scale. He gathered enormous resources through taxation, for various construction projects. The three kings who preceded him were Cambyses (530–522 BC), Bardiya (522 BC), and Darius 1 (522-486 BC).

through his riches, he shall stir up all the realm of Greece – most translations state this as “all against the realm of Greece” but the actual text reads “all אֵת the realm of Greece.” The word אֵת only denotes the accusative and is not translatable. Xerses I caused Greece to covet the riches of Persia. This is similar to the story of Isa 39, where Hezekiah showed Babylon all of his riches. This resulted in Babylon’s attack; as we read in Isa 39:5-6. Xerses I not only flaunted his wealth, but he also unsuccessfully attacked Greece, which eventually resulted in Persia’s fall, by Alexander the Great.
3 A mighty king shall stand up, who shall rule with great dominion, and do according to his will.
Dan 11:3
then a mighty king shall arise – Alexander the Great, as described in Dan 8:5.