I know it feels like this war is really dragging on; but I think that is precisely how Vyasa wanted us to feel by this point in the battle. We are all getting tired of the unending violence. Even the main cause of all the violence, Bhisma, is getting tired of this, and he has begun looking for a way out.
On day 9, the old Kuru apparently relieved himself of the last of his commitments, which was to wipe out the army of the Saumakas. Now the only thing left for him to do was to find the most noble way to meet his death. On the evening of the ninth day, the Pandavas visit their grand-uncle in his tent and walk away with the old man's permission and even blessing to kill him on the tenth day.
So this is it-- Arjun is finally committed to this action, and Sikhandin is put at the head of the attack. By the time they are done, Bhisma is literally a human pincushion. He is impaled by so many arrows that his body does not touch the ground when he finally falls.
Arjun kindly provides a pillow of arrows and a nice little drinking fountain, so Bhisma may wait until the seasons change and the sun finally resumes its northward course in the heavens. Until then, he's content to hang out on his prickly bed and watch the action from the sidelines.