Alexander the Great was a king of Macedonia who conquered an empire that stretched from the Balkans to modern-day Pakistan.

Alexander was the son of Philip II and Olympias (one of Philip's seven or eight wives). He was brought up with the belief that he was of divine birth. "From his earliest days, Olympias had encouraged him to believe that he was a descendent of heroes and gods. Nothing he had accomplished would have discouraged this belief," writes Wellesley College classics professor Guy MacLean Rogers in his book "Alexander" (Random House, 2004).

"The personality of Alexander the Great was a paradox," Susan Abernethy of The Freelance History Writer told LiveScience. "He had great charisma and force of personality but his character was full of contradictions, especially in his later years (his early thirties). However, he had the ability to motivate his army to do what seemed to be impossible."

Alexander was a visionary, said Abernethy. His ability to dream, plan and strategize on a large scale allowed him to win many battles, even when he was outnumbered. It also helped motivate his men, who knew they were part of one of the greatest conquests in history.

Alexander could be inspiring and courageous, continued Abernethy. He was devoted to training his men, rewarding them with honors and spoils, and going into battle beside them, which furthered their devotion and confidence. "The fact that Alexander was young, beautiful and empathetic only helped to increase his influence on his soldiers and subjects," she said.

Yet, despite his military accomplishments, ancient records say that he failed to win the respect of some his subjects and, furthermore, he had some of the people closest to him murdered.

Alexander the prince

Alexander was born around July 20, 356 B.C., in Pella, which was the administrative capital of Macedonia. His father was often away, conquering neighboring territories and putting down revolts. Nevertheless, King Philip II of Macedon was one of Alexander's most influential role models, said Abernethy. "Philip ensured Alexander was given a noteworthy and significant education. He arranged for Alexander to be tutored by Aristotle himself … His education infused him with a love of knowledge, logic, philosophy, music and culture. The teachings of Aristotle [would later aid] him in the treatment of his new subjects in the empires he invaded and conquered, allowing him to admire and maintain these disparate cultures."

Alexander watched his father campaign nearly every year and win victory after victory. Philip remodeled the Macedonian army from citizen-warriors into a professional organization. Philip suffered serious wounds in battle such as the loss of an eye, a broken shoulder and a crippled leg. But he just kept on fighting, something Alexander would do as commander."

Cambridge University professor Paul Cartledge writes in his book "Alexander the Great" (MacMillan, 2004) that Philip decided to leave his 16-year-old son in charge of Macedonia while he was away on campaign. Alexander took advantage of the opportunity by defeating a Thracian people called the Maedi and founding "Alexandroupolis," a city he named after himself. "Alexander felt the need to challenge his father's authority and superiority and wished to out-do his father," said Abernethy.

Indeed, ancient records indicate that the two became estranged later in Alexander's teenage years and at one point his mother was exiled to Epirus. "Alexander may have resented his father's many marriages and the children born from them, seeing them as a threat to his own position," said Abernethy.

Philip II was assassinated in 336 B.C. while celebrating the wedding of his daughter Cleopatra (not the famous Egyptian pharaoh). The person who stabbed him was said to have been one of Philip's former male lovers, named Pausanias. While ancient writers spin an elaborate tale about his motives, some modern historians suspect that he may have been part of a larger plot to kill the king, one that may have included Alexander and his mother.

At the time of his death, Philip was contemplating invading Persia. The dream was passed onto Alexander, partly via his mother Olympias, according to Abernethy. "She fostered in him a burning dynastic ambition and told him it was his destiny to invade Persia."

Upon his father's death, Alexander moved quickly to consolidate power. He gained the support of the Macedonian army and intimidated the Greek city states that Philip had conquered into accepting his rule. After campaigns in the Balkans and Thrace, Alexander moved against Thebes, a city in Greece that had risen up in rebellion, conquering it in 335 B.C., and had it destroyed.

With Greece and the Balkans pacified, he was ready to launch a campaign against the Persian Empire, a campaign his father had planned but, as fate would have it, he would be the one to lead.

War with Persia

Ancient accounts say that when Alexander was at war against the Persians and their king Darius III, he often used the Persian invasions of Greece in the 5th century B.C. as an excuse for his actions. Yet, ironically, Alexander often fought Greek mercenaries while campaigning against Darius III. Even more ironically, Sparta, a city that had famously lost its king and 300 warriors in the Battle of Thermopylae during a Persian invasion attempt, also opposed Alexander, going so far as to seek Persian help in their efforts to overthrow him.

In a recently published conference paper, Elpida Hadjidaki, the past director of Maritime Antiquities in the Greek Ministry of Culture, points out that Agis III, the king of Sparta, worked with the Persians to fortify a harbor at Phalasarna, in west Crete. Persia gave him money and ships and in return "Agis sent the money and triremes [a type of ship] to his brother Agesilaos, directing him to pay the salaries of the crews, and to sail directly to Crete to settle the affairs of the island for the benefit of Sparta," writes Hadjidaki. In his excavations he has found that, with Persian support, the Spartans built fortifications and a larger harbor at Phalasarna.

Yet, despite the opposition from the Spartans, Alexander was successful against Persia. The first major battle he won was the "Battle of Granicus," fought in 334 B.C. in modern-day western Turkey, not far from the ancient city of Troy. During the battle, Arrian wrote that Alexander defeated a force of 20,000 Persian horsemen and an equal number of foot soldiers. He then advanced down the coast of west Turkey, taking cities and trying to deprive the Persian navy of bases.

The second key battle he won, and perhaps the most important, was the Battle of Issus, fought in 333 B.C. near the ancient town of Issus in southern Turkey, close to modern-day Syria. In that battle, the Persians were led by Darius III himself. Arrian estimates that Darius had a force of 600,000 troops (probably wildly exaggerated) and positioned himself initially on a great plain where he could mass them all effectively against Alexander, who hesitated to give battle.

Darius III is said to have thought this a sign of timidity. "One courtier after another incited Darius, declaring that he would trample down the Macedonian army with his cavalry." So, Darius gave up his position and chased Alexander. At first this went well, and he actually got in the rear of Alexander's force. However, when Alexander gave the Persian king battle, it turned out Darius had been led to a narrow spot where the Persians could not use their superior numbers effectively.

Arrian wrote that, against the experienced Macedonian troops, Darius's left wing was "routed" almost immediately. The toughest opposition actually came from a Greek mercenary force fighting for Darius. Positioned in the center the "action there was desperate, as the Greeks tried to drive the Macedonians back to the river and to recover victory for their own men who were already fleeing," Arrian wrote. Eventually Darius III fled, along with his army.

In his haste, Darius III left much of his family behind including his mother, wife, infant son and two daughters. Alexander ordered that they be "honored, and addressed as royalty," Arrian wrote. After the battle, Darius III offered Alexander a ransom for his family and alliance, through marriage, with him.

Arrian said that Alexander rebuked Darius in writing and used the attempts of his predecessors to invade Greece as justification for his campaign against him. He also added that "in the future whenever you send word to me, address yourself to me as King of Asia and not as an equal, and let me know, as the master of all that belonged to you, if you have need of anything."

Into Egypt

Alexander moved south along the eastern Mediterranean, a strategy designed, again, to deprive the Persians of their naval bases. Many cities surrendered while some, such as Tyre, which was on an island, put up a fight and forced Alexander to lay siege.

In 332 B.C., after Gaza was taken by siege, Alexander entered Egypt, a country that had experienced on-and-off periods of Persian rule for two centuries. On its northern coast, he founded Alexandria, the most successful city he ever built. Arrian wrote that "a sudden passion for the project seized him, and he himself marked out where the agora was to be built and decided how many temples were to be erected and to which gods they were to be dedicated…" Recent research indicates that Alexandria may have been built to face the rising sun on the day Alexander was born.

He also travelled to Libya to see the oracle of Ammon. Traveling through unmarked desert, his party made his way to the temple and Alexander is said to have consulted the oracle in private.

Final battle with Darius III

With the eastern Mediterranean and Egypt secured, the Persians were deprived of naval bases, and Alexander was free to move inland to conquer the eastern half of the Persian Empire.

At the Battle of Gaugamela, fought in 331 B.C. in northern Iraq near present-day Erbil, Alexander is said by ancient sources to have faced as many as 1 million troops (again probably grossly exaggerated). Darius III brought soldiers from all over, and even beyond, his empire. Scythian horsemen from his northern borders faced Alexander, as did "Indian" troops (as the ancient writers called them) who were probably from modern-day Pakistan.

Again, in a bid to stymie Darius III's superior numbers, Alexander moved his troops toward unlevel ground. Darius sent his cavalry after them and Alexander countered with his. His horsemen, while taking heavy losses, held their own. Darius responded by sending his chariots against Alexander's phalanx infantry, a bad move, as they were cut to pieces by javelins.

The battle soon became a war of nerves. "For a brief period the fighting was hand to hand, but when Alexander and his horseman pressed the enemy hard, shoving the Persians and striking their faces with spears, and the Macedonian phalanx, tightly arrayed and bristling with pikes, was already upon them, Darius, who had long been in a state of dread, now saw terrors all around him; he wheeled about — the first to do so — and fled," wrote Arrian. From that point on the Persian army started to collapse and the Persian king fled with Alexander in hot pursuit.

Darius III would flee into the eastern part of his empire, hoping to rally enough soldiers for another battle. Betrayed by one his satraps named Bessus (who claimed kingship over what was left of Persia), Darius was captured by his own troops and killed.

Alexander was saddened when he found his dead body. He respected Darius as the head of the mighty Persian Empire, though Alexander regarded himself as a higher authority because he believed his power came from the gods, according to Abernethy. He sent Darius's body back to Persepolis and ordered that he be given a royal burial.

Alexander wanted the transition in Persia from Darius's power to his own to be peaceful. It needed to have the appearance of legitimacy to appease the people, and providing a noble burial for Darius was part of that, explained Abernethy.

"[Providing noble burials] was a common practice by Alexander and his generals when they took over the rule of different areas of empire," she said. Alexander was influenced by the teachings of his tutor, Aristotle, whose philosophy of Greek ethos did not require forcing Greek culture on the colonized. "Alexander would take away the political autonomy of those he conquered but not their culture or way of life. In this way, he would gain their loyalty by honoring their culture, even after the conquest was complete, creating security and stability. Alexander himself even adopted Persian dress and certain Persian customs," said Abernethy.

Alexander pursued Bessus eastward until he was caught and killed. Then, wishing to incorporate the most easterly portions of the Persian Empire into his own, he campaigned in central Asia. It was a rocky, frost-bitten campaign, which raised tensions within his own army and, ultimately, would lead to Alexander killing two of his closest friends.

The killing of Parmerio

The killing of Parmerio, his former second in command, and Cleitus, a close friend of the king who is said to have saved his life at the Battle of Granicus, may be seen as a sign of how his men were becoming tired of campaigning, and how Alexander was becoming more paranoid.

At some point during Alexander's campaign in central Asia, Parmerio's son, Philotas, allegedly failed to report a plot against Alexander's life. The king, incensed, decided to kill not only Philotas and the other men deemed conspirators, but also Parmerio, even though he apparently had nothing to do with the alleged plot.

According to the writer Quintus Curtius (who lived during the first century A.D.), Alexander tasked a man named Polydamus, a friend of Parmerio, to perform the deed, holding his brothers hostage until he murdered him. Arriving in Parmerio's tent in the city where he was stationed, he handed him a letter from Alexander and one marked as being from his son.

When he was reading the letter from his son, a general named Cleander, who aided Polydamus with his mission, "opened him (Parmerio) up with a sword thrust to his side, then struck him a second blow in the throat…" killing him. (Translation by Pamela Mensch and James Romm)

Murder of Cleitus

A second casualty of Alexander's was his old friend Cleitus, who was angry that Alexander was adopting Persian dress and customs. After an episode where the two were drinking, Cleitus told his king off, telling him, in essence, that he should follow Macedonian ways, not those of the Persians who had opposed him.

After the two got drunk, Cleitus lifted up his right hand and said "this is the hand, Alexander, that saved you then (at the Battle of Granicus)." Alexander, infuriated, killed him with a spear or pike.

Alexander took his act of murder terribly. "Again and again, he called himself his friend's murderer and went without food and drink for three days and completely neglected his person," wrote Arrian.

This 1875 map shows Alexander the Great's empire. (Image credit: Steven Wright/Shutterstock)

The final campaigns

Alexander's days in central Asia were not all unhappy. After his troops had captured a fortress at a place called Sogdian Rock in 327 B.C. he met Roxana, the daughter of a local ruler. The two married and, at the time of Alexander's death, they had an unborn son.

Despite the fatigue of his men, and the fact that he was far from home, he pressed on into a land that the Greeks called "India" (although it was actually present-day Pakistan). He made an alliance with a local ruler named Taxiles who agreed to allow Alexander to use his city, Taxila, as a base of operations. He also agreed to give Alexander all the supplies he needed, something important given Alexander's long supply lines.

In exchange, Alexander agreed to fight Porus, a local ruler who set out against Alexander with an army that reportedly included 200 elephants. The two armies met at the Hydaspes River in 326 B.C., with Porus assuming a defensive position on its opposite bank. Alexander bided his time, he scouted the area, built up a fleet of ships and lulled Porus into a false sense of security, having his men make it appear that they were going to cross the river so many times that eventually Porus got tired of responding and just ignored the noise they made.

Alexander selected a spot on the river with a wooded island and, at night, managed to bring his troops across to the opposite bank. When Porus mobilized his forces he found himself in a predicament, his cavalry was not nearly as experienced as Alexander's and, as such, he put his 200 elephants, something the Macedonians had never faced in large numbers, up front.

Alexander responded by using his cavalry to attack the wings of Porus's forces, quickly putting Porus's cavalry to flight. The result was that Porus's horses, foot soldiers and elephants eventually became jumbled together. Making matters worse for Porus, Alexander's phalanx attacked the elephants with javelins, the wounded elephants going on a rampage stomping on both Alexander's and Porus's troops.

With his army falling apart Porus stayed until the end and was captured. Arrian wrote that Porus was brought to the Macedonian king and said "treat me like a king, Alexander." Alexander, impressed with his bravery and words, made him an ally.

The journey home

In 324, Alexander's close friend, general and bodyguard Haphaestion died suddenly from fever. Haphaestion's death caused a drastic change in Alexander's personality, said Abernethy. "Alexander had always been a heavy drinker and the substance abuse began to take its toll. He lost his self-control and his compassion for his men. He became reckless, self-indulgent and inconsistent, causing a loss of loyalty by his men and officers. He had always had a violent temper and been rash, impulsive and stubborn. The drinking made these traits worse.

He began to press his men too hard. The vision was gone, causing the appearance of fighting just for fighting's sake. The soldiers became exhausted, frustrated and lost their purpose. They refused to go further and Alexander was forced to turn back."

Sailing south down the Indus River he fought a group called the Malli, becoming severely wounded after he himself led an attack against their city wall. After reaching the Indian Ocean he split his force in three. One element, with the heavy equipment, would take a relatively safe route to Persia, the second, under his command, would traverse Gedrosia, a largely uninhabited deserted area that no large force had ever crossed before. A third force, embarked on ships, would support Alexander's force and sail alongside them.

The Gedrosia crossing was a miserable failure with up to three-quarters of Alexander's troops dying along the way, his fleet being unable to keep up with them due to bad winds. "The burning heat and the lack of water destroyed a great part of the army and particularly the pack animals," Arrian wrote.

Why Alexander chose to lead part of his force through Gedrosia is a mystery. It could simply be because no one had ever attempted to bring such a large force through it before and Alexander wanted to be the first.

Return to Persia

Alexander returned to Persia, this time as the ruler of a kingdom that stretched from the Balkans to Egypt to modern day Pakistan. In 324 B.C., he arrived in Susa, where a number of his innermost advisers got married.

Alexander took two additional wives in addition to Roxana, whom he had married in central Asia. One was Barsine, daughter of Darius III, and another a Persian woman who Arrian identified as Parysatis. Roxana likely did not take kindly to her two new co-wives and, after Alexander's death, she may have had them both killed.

In 323 B.C., Alexander was in Babylon, his next major military target apparently being Arabia on the southern end of his empire. In June 323 B.C., while he was readying troops, he caught a fever that would not go away. He soon had trouble speaking and eventually he died. (Recent research suggests Alexander may have been poisoned.)

Shortly before his death, Alexander was supposedly asked who his empire should go to. His answer was said to be "to the strongest man." Although he had an unborn son, and according to recent research an illegitimate son named Argaeus, there was nobody strong enough to hold his empire together. His generals fought over his land and in the end it was divided up into multiple states.

In 30 B.C., after the last of these states (Ptolemaic Egypt) was conquered by Rome, the Roman Emperor Octavian went to see the body of Alexander. The great king had been dead for nearly three centuries but was revered by the Romans.

"He (Octavian) had a desire to see the sarcophagus and body of Alexander the Great, which, for that purpose, were taken out of the cell in which they rested and after viewing them for some time, he paid honors to the memory of that prince, by offering a golden crown, and scattering flowers upon the body," wrote Suetonius Tranquillus in the late first century A.D. (Translation by Alexander Thomson, through Perseus Digital Library)

Alexander's legacy

"Perhaps the most significant legacy of Alexander was the range and extent of the proliferation of Greek culture," said Abernethy. "The reign of Alexander the Great signaled the beginning of a new era in history known as the Hellenistic Age. Greek culture had a powerful influence on the areas Alexander conquered."

Many of the cities that Alexander founded were named Alexandria, including the Egyptian city that is now home to more than 4.5 million people. The many Alexandrias were located on trade routes, which increased the flow of commodities between the East and the West.

"Goods and customs, soldiers and traders all mingled together," said Abernethy. "There was a common currency and a common language (Greek) uniting the many peoples of the empire. All religions were tolerated. It was to be a golden age that lasted from the death of Alexander in 323 B.C. until 31 B.C., the date of the conquest of the last Hellenistic kingdom by Rome, the Lagid kingdom of Egypt."

Additional reporting by Jessie Szalay, Live Science contributor.