I am shocked, shocked to see that occasional gun user JJV ("user" defined here as "carries around pointlessly for a day while reading The Federalist Papers in the woods") failed to note the above reply of Leonidas to Xerxes' demand that the Spartans surrender their weapons prior to the Battle of Thermopylae.
I actually found strikingly little to disagree with in this or the last few posts, which immediately worries me. (On the other hand he just posted this, although he wisely does not directly endorse the boneheaded author's boneheaded thesis. It appears that bedtime will be delayed somewhat.) However, the figure of three million given for the size of the Persian army strikes me as Greek propaganda (convenient 10,000-to-one-odds, no?), although the above-referenced Wikipedia article surveys various theories as to how large an army could be supported. Even at the low end of the estimates the Spartan achievement is noteworthy and I do not mean to detract from it.
As a side note, one of the final acts of the Persian War was the Battle of Plataea, in which the Greeks defeated the remaining Persian forces in Greece. Captured Persian weapons were melted to produce a victory trophy, offered to the Oracle at Delphi, in the shape of intertwined serpents. The Roman Emperor Constantine took the trophy with him when he founded Constantinople, and what remains of it may be seen today, as Laura and I did five years ago, in what remains of the Hippodrome in Istanbul (not Constantinople).