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The Agalassoi were a tribe that lived in modern Pakistan in the lower Indus Valley at the time of Alexander the Great. During Alexander's invasion of India, the Agalassoi were defeated in battle by the Macedonian army. The citizens numbering about 20,000 after a brave resistance to Alexender, cast themselves with their wives and children into flames.
Sources
Battacharya, Sachchidananda. A Dictionary of Indian History (Westport: Greenwood Press, 1977) p. 10.