Tatah shankhaashcha bheryashcha
Then (following Bheeshma), conches and kettle-drums, tabors, drums and cow-horns blared forth quite suddenly (from the side of the Kauravas); and the sound was tremendous.
Tatah shvetair hayair yukte
mahati syandane sthitau;
divyau shankhau pradadhmatuh.
Then also, Madhava (Krishna), and the son of Pandu (Arjuna), seated in their magnificent chariot yoked with white horses, blew their divine conches.
RG Purport: At the beginning of a war various bombastic instruments are blown like the conchshells, kettledrums etc. When such instruments pierce the silence of the skies, it indicates that the battle about to commence is inevitable and there can be no back-out after the blowing of conch-shells. Bheeshma being the eldest Kuru blew his conchshell. The sound of the conchshell was tumultuous and was indicative of the personality of Bheeshmadeva. The Kauravas, in order to present their formidable nature sounded kettledrums, cow-horns and tabors. They wanted to create a scare in the hearts of the Pandavas so that they could have a psychological advantage. However the poor fellows were oblivious about the divinity of Lord Sri Krishna whose very presence in the Pandava camp was enough to dispel any doubts of victory for the Pandavas. Thus the Pandavas had already won the war psychologically. Thus whoever impresses the Lord through one’s straight-forwardness and surrender automatically need not fear because the Lord stands in protection of such a living entity. Even if there is a catastrophe awaiting a “jeeva”, the name of the Lord is enough to cast away the darkness of such catastrophe. Lord Krishna and Arjuna had mounted themselves on a chariot presented to Arjuna by the grace of the Lord by Ari Agnideva. The flag mounted on the top of the chariot carried the insignia of Lord Hanuman who himself was part of the victorious battle against Ravana in Treta Yuga. His additional presence on the chariot of Arjuna heralded impregnability. The sound of the conchshells of both Sri Krishna and Arjuna was tumultuous yet divine as if from the spiritual world very much unlike the sounds of conchshells from the Kaurava camp. The chariot of Arjuna of whom the Supreme Lord was the charioteer was drawn by white horses indicating that Dharma in the form of the white horses was waging a war against Adharma represented by the Kaurava camp.