Excerpts from Books and Wikipedia
"In 499, the Ionian city-states began a rebellion against Persia, and they appealed to the Greek city-states for aid. . . . When Darius suppressed the Ionian revolt, he swore revenge on Athens, who had dared to aid the Ionian rebels. . . . This Darius mounted in 490 (some sources argue 491 B.C.), sending 600 ships full of infantry and cavalry to subdue Athens and establish Persian might in Greece. . . . The Greek victory at Marathon was not conclusive, in that it did not keep the Persians away; they returned 10 years later to be defeated at the even more decisive battle of Salamis. . . . As J.F.C. Fuller writes, the victory 'endowed the victors with a faith in their destiny which was to endure for three centuries, during which western culture was born. Marathon was the birth cry of Europe.'"[Davis: 100 Decisive Battles, p. 13]