Darius the Great in the context of "Cyrus the Great"

The Greco-Persian Wars (also often called the Persian Wars) were a series of conflicts between the Achaemenid Empire and Greek city-states that started in 499 BC and lasted until 449 BC. The collision between the fractious political world of the Greeks and the enormous empire of the Persians began when Cyrus the Great conquered the Greek-inhabited region of Ionia in 547 BC. Struggling to control the independent-minded cities of Ionia, the Persians appointed tyrants to rule each of them. This would prove to be the source of much trouble for the Greeks and Persians alike.

In 499 BC, the tyrant of Miletus, Aristagoras, embarked on an expedition to conquer the island of Naxos, with Persian support; however, the expedition was a debacle and, preempting his dismissal, Aristagoras incited all of Hellenic Asia Minor into rebellion against the Persians. This was the beginning of the Ionian Revolt, which would last until 493 BC, progressively drawing more regions of Asia Minor into the conflict. Aristagoras secured military support from Athens and Eretria, and in 498 BC these forces helped to capture and burn the Persian regional capital of Sardis. The Persian king Darius the Great vowed to have revenge on Athens and Eretria for this act. The revolt continued, with the two sides effectively stalemated throughout 497–495 BC. In 494 BC, the Persians regrouped and attacked the epicenter of the revolt in Miletus. At the Battle of Lade, the Ionians suffered a decisive defeat, and the rebellion collapsed, with the final embers being stamped out the following year.

Cleomenes I (/kliːˈɒmɪniːz/; Greek Κλεομένης; died c. 490 BC) was Agiad King of Sparta from c. 524 to c. 490 BC. One of the most important Spartan kings, Cleomenes was instrumental in organising the Greek resistance against the Persian Empire of Darius, as well as shaping the geopolitical balance of Classical Greece.

The siege of Naxos (499 BC) was a failed attempt by the Milesian tyrant Aristagoras, operating with support from, and in the name of the Persian Empire of Darius the Great, to conquer the island of Naxos. It was the opening act of the Greco-Persian Wars, which would ultimately last for 50 years.

Aristagoras had been approached by exiled Naxian aristocrats, who were seeking to return to their island. Seeing an opportunity to bolster his position in Miletus, Aristagoras sought the help of his overlord, the Persian king Darius the Great, and the local satrap, Artaphernes to conquer Naxos. Consenting to the expedition, the Persians assembled a force of 200 triremes under the command of Megabates.

The Ionian Revolt, and associated revolts in Aeolis, Doris, Cyprus and Caria, were military rebellions by several Greek regions of Asia Minor against Persian rule, lasting from 499 BC to 493 BC. At the heart of the rebellion was the dissatisfaction of the Greek cities of Asia Minor with the tyrants appointed by Persia to rule them, along with the individual actions of two Milesian tyrants, Histiaeus and Aristagoras. The cities of Ionia had been conquered by Persia around 540 BC, and thereafter were ruled by native tyrants, nominated by the Persian satrap in Sardis. In 499 BC, the tyrant of Miletus, Aristagoras, launched a joint expedition with the Persian satrap Artaphernes to conquer Naxos, in an attempt to bolster his position. The mission was a debacle, and sensing his imminent removal as tyrant, Aristagoras chose to incite the whole of Ionia into rebellion against the Persian king Darius the Great.

In 498 BC, supported by troops from Athens and Eretria, the Ionians marched on, captured, and burnt Sardis. However, on their return journey to Ionia, they were followed by Persian troops, and decisively beaten at the Battle of Ephesus. This campaign was the only offensive action by the Ionians, who subsequently went on the defensive. The Persians responded in 497 BC with a three-pronged attack aimed at recapturing the outlying areas of the rebellion, but the spread of the revolt to Caria meant that the largest army, under Daurises, relocated there. While initially campaigning successfully in Caria, this army was annihilated in an ambush at the Battle of Pedasus. This battle had started a stalemate for the rest of 496 BC and 495 BC.

The Battle of Lade (Ancient Greek: Ναυμαχία τῆς Λάδης, romanized: Naumachia tēs Ladēs) was a naval battle which occurred during the Ionian Revolt, in 494 BC. It was fought between an alliance of the Ionian cities (joined by the Lesbians) and the Persian Empire of Darius the Great, and resulted in a decisive victory for the Persians which all but ended the revolt.

Around 535 BCE, the Persian king Cyrus the Great initiated a protracted campaign to absorb parts of India into his nascent Achaemenid Empire. In this initial incursion, the Persian army annexed a large region to the west of the Indus River, consolidating the early eastern borders of their new realm. With a brief pause after Cyrus' death around 530 BCE, the campaign continued under Darius the Great, who began to re-conquer former provinces and further expand the Achaemenid Empire's political boundaries. Around 518 BCE, the Persian army pushed further into India to initiate a second period of conquest by annexing regions up to the Jhelum River in what is today known as Punjab. At peak, the Persians managed to take control of most of modern-day Pakistan and incorporate it into their territory.

The first secure epigraphic evidence through the Behistun Inscription gives a date before or around 518 BCE. Persian penetration into the Indian subcontinent occurred in multiple stages, beginning from the northern parts of the Indus River and moving southward. As mentioned in several Achaemenid-era inscriptions, the Indus Valley was formally incorporated into the Persian realm through provincial divisions: Gandāra, Hindush, and Sattagydia.