This is a powerful painting of a burning city near the ocean. The city is in ruins, and the smoke is billowing into the sky. There are soldiers fighting in the streets, and there are bodies lying on the ground.
The image is a depiction of the battle of Samos, which was a real battle that took place in 440 BC. The battle was fought between the Athenians and the Samians, and it ended in victory for the Athenians.