Thin Black Line
They may have had some "internal" concerns of their own at the time.
http://en.wikipedia.org/wiki/Xerxes_...a#In_the_Bible
Ah, the old question - was Xerxes the same Persian Emporer known as Ahasuevos in the Book/Scroll of Esther (i.e. of Purim fame)?
I've been trying for quite some time to link up the Xerxes of Thermopylae with Ahasueros of Purim. There's an apparent gap in time - Thermopylae took place in 480 BCE, and Purim just before the Jews went back to rebuild the Temple. Since the 1st Temple was destroyed in 586 BCE and 70 years passed before the Temple was rebuilt, that would be 516 BCE, some 36 years before Thermopylae. Of course, we cannot know if the date for Thermopylae is 100% accurate - up to the time of the Romans, there was no single Western calendar set up. Further, Jewish tradition has the 2nd Temple standing for 420 years - and destruction in 70 CE means it was built in 350 BCE, some 166 years prior to 516 BCE. This 166 year gap has been the subject of a fair amount of discussion among historians, but it doesn't necessarily mean that Xerxes and Ahasueros were different people - i.e. if the traditional Western dating system is off because of a lack of consistency, then they could be the same person. Also, the 36 year gap discussed above isn't necessarily a gap - many Jews stayed in Persia (i.e. "by the waters of Babylon") even after the Temple was rebuilt, and the area now known as Israel was one of the 127 provinces/satrapies ruled by Ahasueros according to the Book of Esther (so, therefore, the Jews there would have also been subjected to genocide under the decree that Haman got from Ahasueros).
My understanding is that Xerxes and Ahasueros were very similar in character (arrogant, impulsive, insecure, etc.) and ruled the same extremely wealthy and extremely populous nation/empire, so it is at least within the realm of possibility that they are the same person. And, if so, this guy was at least twice a loser, a bearer of the scarlet "L" on his forehead.
Oh, and to stay on topic, it is entirely possible that Jews would have served (albeit probably involuntarily) in the Persian army or navy. Something like 2 million - 3 million Jews were brought to Babylon by Nebuchadnezzar (whose empire was later taken over by the Media-Persia Empire under Cyrus the Great), and the Persian armed forces were made up of men from everywhere in the empire. I doubt that any Jews were in the (not so) Immortals that were Xerxes' personal guard, and I am utterly positive that no Jews were part of the force of 300 Spartans at Thermopylae. The Spartans were pure pagan, and were brutal thugs that engaged in child murder, etc. (yeah, they loved freedom - but only their own). Could Jews have been with the other Greek forces? That's doubtful. The Jews lived in the Kingdoms of Israel and Judah before the 1st Temple was destroyed, and the survivors were exiled to Babylon. That's the other direction from Greece. The fact that there were Greek Jews from the period of the 2nd Temple up through the 20th century is irrelevant to the period immediately surrounding the Battle at Thermopylae.
BTW, even though I have a lot of contempt for the Spartan way of life, I think that those at Thermopylae were heroes who saved not only their own civilization, but also the very idea of the West. I admire them greatly for their heroism, for their willingness to sacrifice themselves for their nation and their people, and I cannot wait to see "300" on an IMAX screen.
MOLON LABE!!!