Conquest of Persian Empire
After Philip’s assassination in 336 BC, he succeeded his father to the throne. He inherited a strong kingdom and an experienced army.
Nobles awarded Alexander with the generalship of Greece. He used this authority to launch his father’s pan-Hellenic project to lead the Greeks in the conquest of Persia.
In 334 BC, he invaded the Achaemenid Empire (Persian Empire) and began a series of campaigns that lasted 10 years.
Following the conquest of Anatolia, Alexander broke the power of Persia in a series of decisive battles, most notably the battles of Issus and Gaugamela.
He subsequently overthrew Persian King Darius III and conquered the Achaemenid Empire in its entirety. At that point, his empire stretched from the Adriatic Sea to the Indus River.
Alexander generally kept the original Achaemenid administrative structure, leading some scholars to dub him as “the last of the Achaemenids”
Invasion of India
After conquering the Achaemenid Empire of Persia, Alexander, launched a campaign into the Indian subcontinent in present-day Pakistan.
The rationale for this campaign is usually said to be Alexander’s desire to conquer the entire known world, which the Greeks thought ended in India.
After gaining control of the former Achaemenid satrapy of Gandhara, Alexander advanced into Punjab. Soon he engaged in battle against the regional king Porus, whom Alexander defeated in the Battle of the Hydaspes in 326 BC.
His army, exhausted, homesick, and anxious by the prospects of having to further face large Indian armies throughout the Indo-Gangetic Plain. They mutinied at the Hyphasis and refused to march further east.
Alexander, after a meeting with his officer, Coenus, and after hearing about the lament of his soldiers, eventually relented, being convinced that it was better to return.
Alexander the Great Empire
Alexander’s most immediate legacy was the introduction of Macedonian rule to huge new swathes of Asia. At the time of his death, Alexander’s empire covered some 5,200,000 km2 (2,000,000 sq mi), and was the largest state of its time.
Many of these areas remained in Macedonian hands or under Greek influence for the next 200–300 years. The successor states that emerged were, at least initially, dominant forces. Historian refereed these 300 years as the Hellenistic period.
The eastern borders of Alexander the Great Empire began to collapse even during his lifetime.