Sri Krishna and Arjuna were marching forward to enemies for attack on an ancient chariot used by Brahma, Rudra, Indra and Varuna respectively for riding during ancient period.
ब्रह्मेशानेन्द्रवरुणान् क्रमशो योऽवहत् पुरा। तमाद्यं रथमास्थाय प्रयातौ केशवार्जुनो॥