The Battle of Artemisium represents a series of engagements that took place in August or September 480 BC. In this battle, the fleets of an alliance of Greek city-states (Athens, Corinth, Sparta, etc.) clashed with the fleets of the Persian Empire (ships led by the famous Xerxes). The land battle of Thermopylae took place at the same time as this battle.
Between 492 and 490 BC, the Persians tried to conquer Greece, but failed. This invasion was ended by the Athenians' victory at the Battle of Marathon. The Persian great king Xerxes then decided to launch a new invasion. The combined armies of the defenders were to be led by the Spartan Eurybiades, but the Athenian fleet was more numerous, so the Athenian general Themistocles took the lead. He decided to block the advance of the Persian land forces in the gorge of Thermopylae and at the same time to prevent the advance of the Persian fleet in the strait of Artemisium.
The Persian army numbered about 1200 ships and the Greek about 280 ships. The Persian ships were large and powerful, while the Greek "triremes" were smaller and weaker. However, they had the advantage of greater speed, agility and, most importantly, they had a "taran" on their bows, which they used to pierce the hulls of enemy ships or destroy their oars.
The Persians were caught in a severe storm on their way to Greece, which destroyed about a third of their ships. When they reached Artemisia, they sent 200 ships around the island of Euboea to ram the Greeks in the back. However, this group of ships was also caught in a heavy storm and almost all of them were destroyed. The rest of the Persian army fought in minor skirmishes with the Greeks for two days.
One of the battles was an attack on the Persians by the Greek troops that no one expected, but it was necessary for the defenders to protect their advancing ground troops. By the third day they were attacking in full force, with both fleets losing about the same number of ships. The defenders could not afford the losses through fewer ships, but they did not give up.
Not long after, the defenders received information that the Greeks had lost the Battle of Thermopylae. Their plan was to win both Thermopylae and Artemisium. And so it was no longer worth fighting at Artemisium and only deepening their losses. The Greek fleet retreated to the island of Salamis (on the way the ships helped evacuate the inhabitants of Athens) and the Persians occupied the abandoned Athens. They subsequently attempted to defeat the remaining Greek fleet, but failed to do so and were themselves defeated in September 480 BC at the Battle of Salamis.