When the Greek city-state of Thebes (not to be confused with the Egyptian city of Thebes) revolted against Macedonian rule, Alexander marched there with his troops and put down the revolution. After winning the battle—one of Alexander’s first major campaigns—the Macedonian conquerors proceeded to torch the city.

Paul Cartledge, a professor emeritus of Greek culture at the University of Cambridge, says one reason Alexander burned Thebes was to warn other Greek city-states: Don’t rebel against Macedonian rule. The strategy didn’t quite work, as Sparta revolted (albeit unsuccessfully) in 331 BCE. By that time, Alexander was in Asia, taking over the Persian Empire.

Alexander’s first major victory against the Persian Empire came at the Granicus River in Asia Minor, or Anatolia, which makes up the western half of modern-day Turkey. In this battle, Alexander invaded Persian territory and fought against the empire’s satraps, or regional governors.

Alexander’s victory established Macedonian rule in Asia Minor, kicking off his invasion of the Persian Empire. It emboldened him to move further into the empire’s territory, coming up against the forces of King Darius III.

Alexander’s first battle against King Darius III, ruler of the Persian Empire, took place in the ancient town of Issus (in what is now modern-day Turkey). Like the Battle of Granicus, this was still on the western edge of the Persian Empire.

“This is very significant, because why would the Persian king decide to come to meet Alexander right on the very west of his empire?” Cartledge asks. He posits that Alexander’s campaign in Asia Minor was “so threatening that Darius decided he, personally, must rally his Persian troops and lead them in a big battle.”

Alexander’s army defeated the Persian soldiers, marking a key victory in his quest to conquer the Persian Empire. Darius survived to face Alexander again two years later in the Battle of Gaugamela.

After decisively defeating Darius at the Battle of Issus, Alexander went to Tyre. Located in modern-day Lebanon, Tyre is one of the oldest continually inhabited cities in history. At the time, Tyre was located on an island surrounded by fortified walls, a challenge for military invaders.

Alexander attacked the city by building a causeway from the mainland to the island, and built siege towers on the causeway from which his troops could attack the city. The siege succeeded, and Alexander took the city. But the causeway he built had another, unintended historical impact. Over time, silt settled around this causeway, helping to form the isthmus that now connects Tyre to the mainland.

Alexander and Darius’ second and final battle took place in modern-day Iraq, in the ancient village of Gaugamela. Although Darius’ army outnumbered Alexander’s troops, Alexander once again defeated the Persian king in battle. With this victory, Alexander claimed control of the Persian Empire. Darius escaped alive, but was murdered in 330 BCE by one of his provincial governors.

“After winning Gaugamela, the Persian Empire—the rest of it—is at [Alexander’s] mercy,” Cartledge says. “It’s only a matter of time, really, before he gets it all physically under his control.”

The ancient city of Persepolis, located in modern-day Iran, was one of the capitals of the Persian Empire during Darius III’s reign. With Darius defeated, Alexander marched his army toward the Persian Gate mountain pass outside the city.

Alexander defeated the Persian troops defending the mountain pass, allowing him to capture and then burn the city of Persepolis. Having gained control of the seat of the Persian Empire, Alexander marched east to establish his rule over the parts of the empire that extended into modern-day Afghanistan, Pakistan and India.

Alexander’s last major military victory came at the Hydaspes River, now known as the Jhelum River, in modern-day Pakistan. There, he fought against King Porus and encountered foes he’d never seen before: war elephants, 200 of which Porus’ troops used in battle. While Hydaspes was the closest Alexander ever came to defeat, his forces ultimately prevailed.

Alexander allowed Porus to remain a local ruler if he pledged loyalty to Alexander, the new king of the Persian Empire. With the eastern border of the empire secured, Alexander returned to the central part of the empire.But he would fight no more. In 323 BCE, Alexander became ill and died in the ancient city of Babylon, located in modern-day Iraq. (The cause of death is unknown.) Because the 32-year-old ruler left no heir or clear successor, his death sparked a series of wars over who would take over his vast empire.