The victory of Athens over Persia at marathon was surprising because
Athens was heavily outnumbered and not considered a dominant military power compared to the mighty Persian Empire. The Persian army was much larger and had a reputation for being formidable. Additionally, the distance between Athens and the Persian Empire meant that the Athenians had to fight in hostile territory, far away from their home base.
Despite these odds, the Athenians managed to secure a decisive victory over the Persians. They utilized a coordinated strategy, with the Athenian hoplites charging into the Persian ranks and breaking their formation. The heavily armored hoplites were able to withstand the Persian arrows and engage in close combat, which proved to be effective in defeating the Persian forces.
The victory at Marathon was also surprising because it marked a turning point in the Greco-Persian Wars. It was the first major Persian defeat, and it inspired confidence in the Greek city-states that they could successfully resist Persian aggression. This victory boosted Athens' morale and contributed to the rise of Athenian power in the following years.
Overall, the victory of Athens over Persia at Marathon was surprising due to the overwhelming odds they faced and the fact that it marked a significant turning point in the Greco-Persian Wars.