What Were the Most Important Battles in Ancient Indian History?

The following battles are the most important in the history of India 

The Mahabharata War, 3102 BC

The Mahabharata war was a great civil war fought among cousins and brothers for the succession of the throne of the Kuru Kingdom, the capital of which was in the region of the modern Delhi, then known as Kurukshetra.

Battle of the Hydaspes (Jhelum), 326 BC

Battle of the Hydaspes (Jhelum) was fought in 326 BC between Alexander and King Porus of Punjab.  Porus was defeated by Alexander who restored him to his kingdom as a vassal.  

Seleucid–Mauryan War, 305 BC

The Seleucid–Mauryan War was fought in about 305 between Alexander’s general Seleucus I Nicator and Chandragupta Maurya, the founder of the Mauryan empire. The battle, that took place in western India, ended in the defeat of Seleucus I Nicator who had to yield parts of what is now Afghanistan to Chandragupta Maurya. . Seleucus I Nicator, in exchange, received 500 elephants. 

Kaling War, 261 BC 

The Kaling War was fought between Ashoka of Mauryan  Empire and Kalinga  Kingdom in 261 B.C. After his victory in the Battle of Kalinga, Ashoka substituted conquest by Righteousness (dharma) in place of the policy of territorial aggression. The battle marks a turning point not only in Indian history but in world history too.

Battle of Venni, 180 AD 

The Battle of Venni was fought between the Chola power under Karikala and the combined forces of the Cheras and the Pandyas. The battle took place at Venni (modern Kovilvenni near Thanjavur in Tamil Nadu) during the Sangam age. The Chola power emerged victorious. 

Battle of Pullalur, 618–19 AD 

The Battle of Pullalur was fought between Chalukya king Pulakesin II and the Pallava king Mahendravarman I resulting in the victory of the former. The battle took place at Pullalur (now in the Kanchipuram district in Tamil Nadu) in about 618–19. The Pallava capital Kanchipuram was destroyed. 

Battle of Manimangala, 640 AD

Battle of Manimangala was fought in 640 AD between Pallava ruler Narasimhavarman I and Chalukya king Pulakesin II who suffered defeat. 

Battle of Vatapi, 642 AD

The Battle of Vatapi took place in 642 AD between Pallava ruler Narasimhavarman I and Chalukya king Pulakesin II near the Chalukya capital of Vatapi.  After the battle which resulted in the defeat and death of Pulakeshin II,  Narasimhavarman I took the title of Vatapikonda (Conqueror of Vatapi).