Thats correct. Mahabaratha started with a dog's story, ended with a dog. Also the intresting point is one of the greatest turning point in Mahabaratha in middle was also due to a dog (Ekalavya's episode).
Ugarshavasuvu, goes to niamishaaranya, where sounkaadi maharshi and others were performing dheerga satra yaga (12 years). Ugrashravasuvu is a sishya of vedavyasa (the current vysa's name is krishna dvaipayana). Vedavyasa divided vedas into 4 parts, rig, yajur, sama and atharva. after which he wrote 18 maha puranas. He wrote Mahabaratha after completing puranas. Mahabaratha is also called panchama veda (5th veda).
Sounakaadi maharshi and other ask Ugarshavasuvu where he is coming from then he tells them that he visited Samanthaka panchakam and Janamejaya's yagashala. Janemejaya is the son of parikshith, grandson of Abhimanyu and great grandson of Pandavas.
So Ugarshavasuvu starts describing about his visit to Janemejaya's yagashala. This is where Mahabharata starts. Janemejaya was performing a yaga for the welfare of his country/people. outside the yagashala a small dog ( you can call it a pup) out of curiosity was looking at what is going on. This pup is the son of sarama ( a deva shuni or a celestial female dog). If a dog enters the yagashala then devatas dont accept the offerings made in the yaga. So Janamejaya's three brothers Shrutasena, Ugrasena, Bhimasena closind in on the pup didnt let it escape and trashed it inflicting lot of pain.
So this poor pup goes and cries and tells its mother that I didnt go inside and didnt do any harm to anyone near the yagashala, but these rajakumaras beat me so much not even letting me escape.
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