It is frequently yelled/screamed/shouted/bellowed just prior to smashing into the ground at unholy speeds or as a wild battle cry before plunging head-first into an impossible battle. When combined with a question mark it becomes a question, quite reminiscent of the sounds monkeys make when establishing the well-being of other monkeys. With fewer aaaaaaaaaaaaa's it becomes a less powerful exclamation of adrenaline-fuelled anger/insanity, suitable for minor tasks, such as battles involving units of people at merely platoon level, rather than hordes.
Bajaaaaaaaaaaaa! We go to battle!
Baja? Is there something wrong?