The biggest what are you talking about.
The Persian Empire was primarily conquered by Alexander the Great in the 4th century BCE. After a series of decisive battles, including the Battle of Granicus, the Battle of Issus, and the Battle of Gaugamela, Alexander defeated the Persian king Darius III. Following Darius's defeat, Alexander continued to expand his empire into Persian territory, ultimately leading to the fall of the Achaemenid dynasty.
Darius I, also known as Darius the Great was defeated in the Battle of Marathon.
Darius I
The Athenian militia defeated the the Persian forces of Darius I.
The death of Darius III was pivotal for Alexander's conquest of Persia as it effectively removed the central figure of Persian resistance, destabilizing the Persian Empire and undermining its leadership. Darius's assassination by his own men highlighted the disarray within the Persian ranks, which allowed Alexander to exploit the resulting power vacuum. Without a unifying leader, the Persian forces struggled to mount a cohesive defense against Alexander's well-coordinated military strategies. Consequently, Darius's death accelerated the collapse of Persian authority and facilitated Alexander's swift victories across the region.
Notably , it was Alexander the great , the king of Macedon who defeated the Persian king Darius the 3rd .
The Persian army of Darius III.
Alexander The Great
Alexander the Great and his Macedonians defeated the Persian armies of Darius III at Gaugamela.
The Persian leader defeated by the Greeks was Darius.
He didn't, Darius' own nobles killed him. Alexander was angry at such and act and killed the killers.
Darius I, also known as Darius the Great was defeated in the Battle of Marathon.
Alexander defeated Darius(?) the King of Persia, who was by the way, murdered by his own bodyguards. Alexander moved on til he occupied the city and palace of the Persian kings and was there declared the new King of that country.
King Darius III got defeated by Alexander the Great and by other conquerors who I don't know about
Darius III.He defeated Darius III 13 times in battle.
Darius I
The Athenian militia defeated the the Persian forces of Darius I.