The Pandavas have come out of hiding and are demanding their lands back from the Kauravas. Duryodhana has already indicated that he has no interest in giving these back, so it would be best to negotiate from a position of strength. An arms race ensues, with both sides scrambling to get commitments from their allies across India and beyond.
Duryodhana wins the first couple of rounds at this game. He rushes to Dwaraka, and gets Krishna to commit his armies to the Kaurava side. The Pandavas get Krishna; as an unarmed advisor. Duryodhana also plays on the generosity of the Pandavas' ally King Shalya, by providing hospitality to Shalya's army while it was on the march. When Shalya offers a boon to his host, Duryodhana presents himself, and asks for Shalya's support in the war. The king has no choice but to grant the request.
The king journeys on to meet with the Pandavas and tells them what had happened. Since Duryodhana fooled them fair & square, Yuddistira accepts the fait accompli. He only asks that Shalya do whatever he can to throw Karna off his game when the big chariot duel between Arjun & Karna takes place.
Shalya also takes the sting off a bit by telling the story of Indra's Victory. This is a strange story in which the brahmins completely dominate the course of events. A brahmin picks a fight with Indra, and although Indra acts in self-defense, he is nevertheless guilty of brahmin-murder, and he suffers accordingly. The force of the punishment makes Indra sort of resign his post and go into hiding.
The Man-God Nahusha is then nominated king of heaven (by brahmins & gods), and the brahmins give him his very own superpower. When Nahusha turns out to be a power-hungry lecher, the brahmin priest Brhaspati advises the gods on how to get their old Indra back. Indra is powerless at this point, so he suggests to his wife that the best way to take down Nahusha would be to get him into a fight with the brahmins. Nahusha walks right into the trap, makes himself a brahmin-drawn chariot, and ends up offending the entire race of priests. It's all over when he specifically annoys Agastya, and gets cursed to life as a snake for 10,000 years. It seems that in this story the "kshatriya" gods are just pawns in a brahmin game!
Finally, the Pandavas and Kauravas have gathered their allies-- 7 grand armies for the good guys, and 11 armies for the bad guys. Now the negotiations can commence!