Hrisheekesha (Krishna) blew Panchajanya; Dhananjaya (Arjuna) blew Devadatta; Vrikodara (the performer of terrific deeds, Bheema) blew his great conch Paundram.
Sanjaya wilfully describes the war cries of the Pandava army in detail, in contrast to what he did earlier for the Duryodhana army.
When Bheeshma blew his conch, Krishna unhesitatingly reciprocated first, by blowing his Panchajanya. Instantly Arjuna blew his Devadatta and Bheema blew his Paundram.
Pandavas did not have either the heart or the will and merit to battle against Bheeshma, their unconquerable grandfather, who was all fondness and benediction for them.
Sensing their reluctance, Krishna gave them and their army the timely lead. But it did not, however, mean violation of his pledge not to wield weapons in the war. War cries mark the readiness and beginning of war, but do not mean actual battling.