The Mahajanapadas and Rise of Magadha

By the 6th century BCE, the Buddhist text Anguttara Nikaya lists 16 Mahajanapadas (great territorial states) spread across northern India, marking the transition from tribal chiefdoms to organised territorial monarchies (and some republics/ganasanghas).

Rise of Magadha: Among the Mahajanapadas, Magadha emerged supreme due to fertile land, iron-ore deposits nearby (for weapons and tools), control over trade routes, elephants for the army, and the strategic capital at Pataliputra (fortified by rivers Ganga, Son, and Punpun).

• Haryanka dynasty: Founded by Bimbisara (contemporary of the Buddha, matrimonial alliances with Kosala, Vaishali, Punjab), succeeded by his son Ajatashatru (who imprisoned his father, fought and defeated the Vajji confederacy using the war engine "rathamusala" and the weapon "mahashilakantaka," and hosted the First Buddhist Council).
• Shishunaga dynasty: Founded by Shishunaga; destroyed the power of Avanti.
• Nanda dynasty: Founded by Mahapadma Nanda, called "Ekarat" (sole sovereign) and "destroyer of all Kshatriyas." The Nandas built a vast empire and a huge army; the last Nanda ruler, Dhana Nanda, was defeated by Chandragupta Maurya with the help of Chanakya (Kautilya/Vishnugupta).

Persian and Greek Invasions

• The Achaemenid ruler Darius I annexed parts of the Indus region (Gandhara/Sindh) around 518 BCE, making it a satrapy of the Persian Empire — this brought Kharosthi script (derived from Aramaic) into India.
• Alexander of Macedon invaded India in 326 BCE, defeating King Porus (Puru) in the Battle of the Hydaspes (Jhelum), but was impressed by his valour and reinstated him as a satrap. Alexander's troops refused to advance further at the river Beas (Hyphasis), forcing his retreat; he died at Babylon in 323 BCE. The invasion opened land trade routes between India and the Hellenistic world and provides valuable synchronistic dating for Indian history.