Daniel 11:2 - Matthew Poole's English Annotations on the Holy Bible

The truth: this is that thing which Daniel saith, Daniel 10:1, was revealed unto him, and was true, i.e. plain, without any obscurity, and should suddenly and certainly come to pass. There shall stand up yet three kings in Persia; which notes their flourishing and strength; for after them that monarchy declined. These three are Cyrus, Smerdis, Darius Hystaspes. Others put Cambyses for Cyrus; others add Xerxes, who is added as the fourth in this same verse, and made more potent than all the other three, because his father Darius had gathered an incredible mass for him, and he also himself drove the same trade for six years together before he made his expedition against Greece. There were more kings of Persia besides those four, but they had no concern with the people of God; but those four had, either in hindering or helping the building of the temple, and therefore the angel's instructions from God to Daniel were principally touching those four who are mentioned. The fourth shall be far richer than they all: he had vast territories from India to Ethiopia; he had a navy of one thousand two hundred ships, and an army of eight hundred thousand, as Ctesias writes, but Herodotus speaks of a prodigious army that Xerxes had little short of five millions and a half, (five millions two hundred and eighty-three thousand,) and all against the realm of Greece, where he made incredible havoc at Thermopyle and Athens, as the Greek and Latin histories mention.