Alexander the Great conquers Persia | World History | Khan Academy

So, where we left off in the last video, we had Alexander the Great consolidating his power over the Macedonian Empire. In particular, he puts down a rebellion in Thebes, destroys the city, which makes the other city-states of Greece say, "Hey, we're not going to mess with this person anymore." Then, Alexander says, "I am now going to conquer Asia. I'm now going to conquer the Persian Empire; do what my father wanted to do before he died."

So, he puts one of his father's generals, now one of his generals, in charge of Greece. Antipater declares him regent and then leads troops off to what many people say is the greatest, or many historians call the greatest adventure of all time: his attempt to conquer the Persian Empire and become the king of Asia.

The year is 334 BCE, and the first major battle that Alexander and his army encounter is at the Granicus River, here in modern-day Turkey. Now, keep in mind that Alexander's force, depending on what time we're looking at, numbers between 40,000 and 50,000 troops—a good number of them infantry, some cavalry. Most of the battles that we'll see him fight, especially the next two against the Persian forces, he's hugely outnumbered. But at Granicus, he has an advantage in terms of the number of infantry. He's slightly outnumbered in terms of cavalry, but he's able to defeat the Persian forces.

These Persian forces are significant; they're led by the Persian satraps. These are the governors of the territories, I guess you could say the Persian regions or provinces in this area in Asia Minor, and he's able to defeat them. But as important as Granicus is, Alexander still has not come directly against Darius III. Darius III is the Shahanshah, the King of Kings, the King of Persia. And not to confuse Darius III with the Darius who, 150 years before this, attacked Greece.

Now you have Alexander, his first decisive victory against the Persians. He makes his way down the Anatolian coast; in his mind, he liberates many of these cities that used to be Greek cities. If we zoom in a little bit, you can see the way this map is set up. So let me zoom in a little bit. Where you see these dotted lines around a city, this means that Alexander's forces sieged the city. They surrounded it; they didn't let anything go in or out until the city surrendered.

You see this path of Alexander and his forces. We then go into 333 BCE. Outside of the forward movement of Alexander's troops and their ability to take over all of Asia Minor, modern-day Turkey, in only a matter of a little more than a year, what also happens in 333 BCE—since some of you might have been wondering, "Well, whatever happens to Sparta?" Philip of Macedon never took over Sparta. Do they stay independent forever? The simple answer is no. In 333 BCE, Antipater defeats the Spartans at the Battle of Megalopolis and forces them into what we now call the League of Corinth.

Let's keep now going back to where Alexander is. Antipater clearly was competent at maintaining power in Greece, and the next major battle that Alexander and his troops face is at Issus. What makes Issus significant is that they are hugely outnumbered. Historians disagree about how much outnumbered. Remember we said Alexander's forces were around 40,000 or 50,000, while the Persians at Issus, depending on which account you look at, were at least 150,000—probably over 100,000. More ancient accounts talk about many hundreds of thousands or even a million troops.

What also made Issus significant is this is the first time that Darius III, the Shahanshah, the King of Persia, directly confronts Alexander. Well, Alexander, once again, is able to overcome unlikely odds and defeat the Persian army, sending Darius into retreat. He retreats so fast that he even leaves an encampment where his mother, his wife, and his two daughters are there. Alexander then takes them captive but treats them very nicely and then eventually marries one of the daughters.

So, after that defeat, Darius is on the retreat, and after that defeat for Darius, this victory for Alexander, Alexander then goes on into the Levant—modern-day Syria, Lebanon, and Israel—and Palestine. You can see he lays siege to the towns of Tyre and Gaza, but by the time he gets through that, it's now 332, and he makes his way into Egypt. He's relatively unopposed; the satraps in Egypt say, "Okay, you know what? We recognize you." They treat him as a liberator.

He takes a pretty large detour to go to the Oracle for the god Amun, and there he is reassured that he is the son of Amun. He is already told by his mother, Olympias, that he is the son of Zeus. So, many people call Alexander—or he calls himself now—Alexander Zeus Amun, the son of Zeus Amun. Once again, he's trying to really make himself, or maybe he believes himself, that he is half-god, that he is a demigod.

But then he continues on with this, I guess you could say, grand adventure. I don't want to romanticize it too much because, even though he is, in some way, conquering and/or unifying these large areas, there's also a lot of bloodshed—a lot of civilians dying. This is a very ugly thing that only looks romantic from maybe a distance of many thousands of years. When you think about it, it would not have been very pleasant to live in any of these cities that Alexander and his troops are going through.

Then he leaves Egypt, and the whole time after the defeat of Issus, Darius keeps sending him entreaties to say, "Hey, maybe we can work this thing out. Maybe you can just stop to the west of the Euphrates. I'll give you this or that." But Alexander keeps saying, "Nope, not for me. I want to be the king of Asia. There's only one king of Asia." So they eventually meet again at Gaugamela—once again, a very significant battle in history where, once again, Darius is there and has a significant force advantage over Alexander.

This time, he doesn't make the mistake of meeting him in a relatively narrow area where his force advantage won't really be an advantage. But even at Gaugamela, Alexander is able to decisively defeat him, and Darius has to flee over the mountains to Ecbatana. My apologies because I know I'm probably not pronouncing it perfectly. Alexander and his forces then go on to capture Babylon and Susa. Susa was actually one of the capitals of the Achaemenid Empire.

So this whole way, they're able to get all of this treasure and start sending it back to Greece. By this point, having been defeated at Issus and now Gaugamela and being on the run, the Persian Empire is, you could say, it's already fallen or it's definitely falling. But it becomes really official once we get to 330 BCE. Remember, this is less than five years since Alexander started, and that's short by any time frame. But they're on foot and on horseback; this is not modern warfare where they have tanks, trucks, and planes.

The fact to conquer so much territory in an empire over 200 years old in this short amount of time frame is kind of breathtaking. But it's in 330 where the forces go to the Achaemenid capital of Persepolis, the capital for over 200 years, and they sack that town. Not only do they sack that town; they destroy the town. I'll repeat it again: Alexander the Great. He's romanticized a lot; he's called "the great," but they destroy that town in a way that you would not make your parents proud, let's just put it that way.

But at that point, he is now king of the Persian Empire. Darius is officially on the run, and what Alexander now cares about is continuing this adventure. Continuing it east into what we now consider to be Afghanistan, Turkmenistan, Uzbekistan, and modern-day Pakistan. He also wants to get Darius. Some would argue he wants to kill him himself; some would argue that he wants to somehow have Darius declare Alexander as the rightful Shahan Shah, king of Asia.

You can see the path of Alexander and his forces. After they destroy Persepolis, they then go up; they turn northwards, and they go through all of these cities up here. Then in 329, they're following the trail of Darius. Darius eventually gets captured and killed by one of his satraps—someone by the name of Bessus. Bessus, who is one of the satraps of Bactria, killed Darius and declares himself Artaxerxes V—the Shahanshah.

Well, eventually, Alexander catches up with Bessus in 329. He's really angry that Bessus has killed Darius. He's also likely angry that Bessus is claiming that he's the Shahanshah. So, he kills Bessus in fairly brutal form. There are different accounts of how the killing happened, but all of them are various degrees of brutal. From there, Alexander's troops continued on eastward—continued on eastward into what we now consider to be Afghanistan and Pakistan.

There, he has the famous battle with the king of Porus, where he encounters these 200 war elephants. But once again, he's this great military tactician, and he's able to defeat the king. Along this whole way, it's worth mentioning he sets up all of these towns—he sets up 20 Alexandrias. Near here, he even sets up a town named after his horse, Bucephalus—the town of Bucephala.

Alexander is eager to keep conquering. Once he defeats the king of Porus, he says, "Hey, I want to go conquer the rest of India." But his troops are far from home, and they're tired. They're spread thin, and they're getting sick. They're not so interested in that. So, eventually, Alexander says, "All right, I’m with y’all. Let's go back." And the troops are really, really happy. They make their way back.

You can see the path back after they—it’s clear they followed the Indus River in Pakistan. Eventually, we get to 323 BCE. Alexander is back in Babylon, and it's over there in Babylon that Alexander dies at the ripe old age of 32. It's mindblowing to think about how much happened in the 12 years that he was emperor of the Macedonians or even the Shahanshah of Persia. He was able to defeat an empire over 200 years old.

What's significant about this is that as he conquered, he encouraged his troops to assimilate. In fact, he was criticized for maybe assimilating a little bit too much. But he dies in Babylon, and it's not clear exactly why he dies. He was a major drinker; some people say alcohol poisoning, some people say it was direct poisoning. But needless to say, this was one of the most significant decades in human history—this conquest of Alexander the Great.