Alexander the Great was born to Basileus (emperor) Philip of the Argead dynasty and Olympias in Pella during 356 BC. His given name was Alexander III but his achievements won him the title of Great. His conquest of large tracts of the Asian continent and parts of North Eastern Africa was a feat unmatched in all of the ancient world.
On the death of Philip, the Greek states raised their banner of revolt and Athens even declared sovereignty. Alexander subdued all the rebels and his razing of the city of Thebes drilled some sense into the Athenians who promptly sued for peace allowing Alexander to plan his Asian advance.
The Persian Campaign
Persia is modern day Iran and was ruled by Darius III of the Achaemenid dynasty. Alexander made a dramatic entry into Asia by flinging a spear into the soil and proclaiming that Asia was a gift from the gods to him. His army consisted of 100,000 odd soldiers from different parts of the Greek city states and included over 100 ships. His first encounter with the Persians was at Granicus where he promptly stated them and sacked the city. He then proceeded to Miletus us and laid siege to the city and ultimately conquered it as well. Alexander traveled along the Ionian coast and conquered one city after the other. His first major siege was at Halicarnassus which was defended by a Greek mercenary from Rhodes. Defeating these forces, Alexander moved onwards towards the heart of the Persian empire with the aim of completely conquering it. His military strategy was such that he kept marching along the coastline to blunt the ability of the Persian empire to use its navy. On reaching Gordium, a Phrygian city, he was presented with the famous Gordian knot which was unsolvable by all except the true king of Asia. Alexander drew his sword and cut it down, thus undoing the knot in the most fashionable way.
The Syrian Campaign
Having traversed Persia, Alexander marched into Syria and the Levant territories subjugating one city after the other. He first met Darius III on the battlefield at Cilicia and tasted defeat for the first time. Without getting disappointed, Alexander retreated and regrouped his soldiers to face Darius III again at Issus. This time, Alexander won a decisive victory and the Persian emperor fled from the battlefield leaving behind his family and his vast treasury. Darius III offered to sue for peace by granting a very generous booty but Alexander wanted to conquer the entire world and so he refused. On reaching the city of Tyre, Alexander treated it really cruelly, razing the city to the ground, killing all the men and selling the women and the children into slavery.
The Egyptian Campaign
The tales of Alexander's antics at Tyre had reached Egypt and many cities submitted to his authority without any resistance. Only the city of Gaza resisted his advances but was ultimately defeated as well. Following his policy used at Tyre, Alexander put to sword all adult men and sold to slavery all the children and women. He marched onwards to reach the Libyan desert where he was proclaimed the liberator of the people by the Oracle at the Siwa oasis. It was here that he founded the city of Alexandria - by - Egypt which went on to become the capital of the Ptolemaic empire.
The Mesopotamian Campaign
By 331 BC, Alexander had marched out of Egypt and reached Mesopotamia (modern day Iraq) and reached the final stronghold of Darius III. Massive armies of both sides clashed once again, this time on the battlefield of Gaugamela. The Persian king was once again routed thoroughly and he fled the battlefield again.
Alexander reached the ceremonial capital of the Persian empire, Persepolis which was the seat of the erstwhile Xerxes I. In the loot and din raised by the invading army, coupled with the flowing alcohol and debauchery, a massive fire broke out in the city. While historians are divided over whether Alexander tried to prevent it or stayed indifferent, the city fell down to the fire amid great destruction.
As Alexander advanced, the control of Darius III over his empire was fast depleting. Darius III was taken prisoner by his own Bactrian satrap Bessus and stabbed to death on his command. Bessus would later declare himself the heir of Darius III and can himself Artaxerxes I. He retreated to Central Asia and harassed Alexander by employing guerilla tactics of warfare.
Alexander considered himself to be the successor of Darius III and chased Artaxerxes I into Asia Minor where he got embroiled with the Scythians under Spitamenes. After a tough battle, the Scythians were defeated and they soon sued for peace.
The Indian Campaign
Having heard many tales of Indian riches, Alexander decided to cross the Hindu Kush mountains and launch a campaign against India. He first met King Ambhi of Taxila, whose empire lay between the rivers Indus and Jhelum. Determined to make friends with Alexander, Ambhi took various pains to ensure it. He built a bridge over the river to help the Greek soldiers cross over and sent lavish gifts and refreshments for the war weary Greek soldiers. Pleased by his demeanor, Alexander chose to not fight a battle against him and picked him as a satrap to further his Indian advance.
As Alexander pushed forward, he faced stiff resistance from erstwhile Persian satrapies in India, Assakenoi and Asapasioi. Both these armies were thoroughly defeated and their cities razed to the ground for their disobedience. Alexander also faced tribal forces of Ora, Massaga, Guraeans and Aornos. Leading personally from the front, Alexander received a deep wound on his shoulder but that did not stop him and he pressed on to defeat ask these tribes.
The next kingdom in Alexander's path was that of King Paurava who refused to submit to Alexander. Both armies clashed on the banks of river Jhelum in the battle of Hydaspes. Despite the numerical superiority of Paurava and his war elephants, the swift battalions of Alexander assisted by the slippery rains routed the Indian army thoroughly. When brought before Alexander in chains, Paurava was asked how would he like to be treated. Paurava replied, “As a king treats another king” which impressed Alexander who returned his territories in lieu of Paurava accepting his vassalage.
Wanting to press further into India and cross the River Ganges, Alexander wanted to crush the might of the powerful Nanda kingdom of Magadh. However, the Greek army revolted near Jhelum itself and beseeched Alexander to let them return home to their families.
Accepting the wishes of his people, Alexander marched back and divided his army under his generals allowing them to take the shorter sea route to Greece. He meanwhile took the harder land route at the head of a much depleted force.
By 326 BC, Alexander had reached the city of Susa and realized that many of his generals had misused their powers. He executed or punished all of them depending on the severity of their transgressions. It was here that Alexander fell ill to malaria that would ultimately be the cause of his death.
Alexander marched further to reach Babylon, his favorite city and took to the bed. He had grown pretty weak and infirm due to his malaria. It was here that he breathed his last after forgiving all the debts of his soldiers and attempting to unite the Greeks and the Persians into an indomitable force. Alexander died in 323 BC at the age of 33 years having carved for himself the biggest empire the ancient world had ever witnessed.
Legacy
While Alexander left behind a vast empire, he could not consolidate it due to his untimely death. His generals who he had entrusted with keeping his empire intact began infighting and weakened the empire. In fact, his own sons began a war of succession further weakening Macedon which ultimately lost in the Third Macedonian War.
However, all was not bad and his influence still lingers on in the form of culture and military tactics. His foray into India led to the development of the Gandhara school of art that added a distinct Hellenistic attribute to their sculptures. Military tacticians even today study and teach the military tactics of Alexander.
He founded multiple cities named Alexandria, the chief among them being Alexandria-by-Egypt. He also founded two cities in both sides of the Jhelum River and named them Bucephala (after his faithful horse) and Niacia (Victory).
In sum, Alexander's conquests led to the fusion of the Greek, Persian, Egyptian, and Indian cultures that expressed itself in arts and architecture. His military prowess and ideology of warfare was quite opposite to the policy of diplomacy of his father, Philip II. The generals he entrusted with the task of managing his foreign territories adopted the cultures of their adopted territories and colored the culture and lifestyle of these regions for years to come.