Darius I, the Great (Old Persian: Dārayava(h)uš) (550–486 BCE), formally known as Darius the Great, was the third king of the Achaemenid Empire. He held the empire at its peak, when it included much of West Asia, the Caucasus, Central Asia, parts of the Balkans (Bulgaria-Romania-Panonia), portions of north and northeast Africa including Egypt (Mudrâya), eastern Libya, coastal Sudan, Eritrea), as well as most of Pakistan, the Aegean Islands and northern Greece/Thrace-Macedonia.

Darius ascended the throne by overthrowing the alleged magus usurper of Bardiya with the assistance of six other Persian noble families; Darius was crowned the following morning. The new king met with rebellions throughout his kingdom and quelled them each time. A major event in Darius's life was his expedition to punish Athens and Eretria for their aid in the Ionian Revolt and subjugate Greece. Darius expanded his empire by conquering Thrace and Macedon and invading Scythia, home of the Scythians, nomadic tribes who invaded Media and had previously killed Cyrus the Great.

Cyrus II of Persia (Old Persian: Kuruš (c. 600 BC or 576 BC–530 BC), commonly known as Cyrus the Great, also known as Cyrus the Elder, was the founder of the Achaemenid Empire. Under his rule, the empire embraced all the previous civilized states of the ancient Near East, expanded vastly and eventually conquered most of Southwest Asia and much of Central Asia, parts of Europe and the Caucasus. From the Mediterranean sea and Hellespont in the west to the Indus River in the east, Cyrus the Great created the largest empire the world had yet seen. He also pronounced one of the first historically important declarations of human rights via the Cyrus Cylinder sometime between 539-530 BCE.

The reign of Cyrus the Great lasted between 29 and 31 years. Cyrus built his empire by conquering first the Median Empire, then the Lydian Empire and eventually the Neo-Babylonian Empire. Either before or after Babylon, he led an expedition into central Asia, which resulted in major campaigns that were described as having brought "into subjection every nation without exception". Cyrus did not venture into Egypt, as he himself died in battle, fighting the Massagetae along the Syr Darya in December 530 BC. He was succeeded by his son, Cambyses II, who managed to add to the empire by conquering Egypt, Nubia, and Cyrenaica during his short rule.

Alexander III of Macedon (20/21 July 356 – 10/11 June 323 BC), commonly known as Alexander the Great (Greek: Ἀλέξανδρος ὁ Μέγας, Aléxandros ho Mégas from the Greek αλέξω alexo "to defend, help" + ανήρ aner "man"), was a king of Macedon, a state in northern ancient Greece. Born in Pella in 356 BC, Alexander was tutored by Aristotle until the age of 16. By the age of thirty, he had created one of the largest empires of the ancient world, stretching from the Ionian Sea to the Himalayas. He was undefeated in battle and is considered one of history's most successful commanders.

Alexander succeeded his father, Philip II of Macedon, to the throne in 336 BC after Philip was assassinated. Upon Philip's death, Alexander inherited a strong kingdom and an experienced army. He was awarded the generalship of Greece and used this authority to launch his father's military expansion plans. In 334 BC, he invaded Persian-ruled Asia Minor and began a series of campaigns that lasted ten years. Alexander broke the power of Persia in a series of decisive battles, most notably the battles of Issus and Gaugamela. He subsequently overthrew the Persian King Darius III and conquered the entirety of the Persian Empire. At that point, his empire stretched from the Adriatic Sea to the Indus River.