Sanjay tells Dhritarashtra: King Drupada, Draupadi's five sons, and the mighty-armed Abhimanyu — all of them blew their conches, each one separately. The conch is a call to war, like a bugle sounding in a modern army. From every corner of the Pandava formation, the sound rose.
Abhimanyu is called "mahabahu" — mighty-armed. Young as he was, the son of Arjuna and Subhadra was already known for extraordinary valor. Later in the war, his courage inside the Chakravyuha would become one of the Mahabharata's most remembered episodes.
With this shloka, the Pandava conch-blowing is complete. Every warrior has announced his presence. The combined sound of all those conches filled the battlefield from horizon to horizon.