This was a grave offense in the eyes of the Persians. However, Athens and Sparta refused to become tributaries and they killed the Persian emissaries. The vast majority of the Greek ‘Polis’ or city-states agreed to accept Darius as their overlord in order to avoid a full-scale Persian invasion.

Darius sent ambassadors to all of the Greek City-States demanding that they do homage to Persia and become tributaries. Darius already controlled many Greek City-States in his empire. The Persian monarch Darius I, was eager not only to punish the Athenians and the Eretrians but also to bring the entire Greek world under his sway. They intended to use Macedonia as a base for an attack on Greece. The Persian, under Mardonius, also conquered Thrace. This invasion army was able to subjugate the Kingdom of Macedonia, which had strong links to the Greek City-States. The first campaign was conducted by land and it involved a Persian army advancing from modern Turkey into the Balkans. The Persian invasion consisted of two distinct phases. The Persians after a difficult fight regained control of Ionia and punished the rebels. They had sent a fleet of ships to the aid of the Ionians.

The Ionian Greeks had revolted against their Persian overlords and they had received the active support of the Athenians. The cause of the invasion was that the Athenians and their allies the Eretrians had supported the Greek city-states in Ionia (west-coast of Turkey). The first Persian invasion of Greece began in 492 BC. The Persian invasion and its subsequent defeat meant that Athenian democracy was strengthened, it led to a cultural flourishing, changes in the military and the development of a large Athenian navy. The impact of the invasion on Athens was profound and it energized the city-state. The first Persian Invasion of Greece was almost a complete success apart from the defeat at Marathon. It was also an effort to spread the influence of Persia throughout the Aegean Sea and into Greece. The First Persian Invasion of Greece was an attempt by the Persian Empire to punish Athens and Eretria for their involvement in its internal affairs. Persian warriors from a monument in Persepolis

The persian expedition