 Why would the Furry Ones not follow Rolf and the others when the retreated?
Rolf swung the lax controls over hard as the bursts of fire revealed a looming barrier of stone dead ahead, and then he felt the tough skin of the flyer crumple inward. Toward this barrier the spinner bore him, and Rolf was content to let it move in that direction—from the heights of the wall he could scout out the country beyond. The spinner had slowed its speed; it seemed to Rolf that he must be falling free in space for a time, but the feeble gravity of the tiny world tugged at him more strongly as he neared the wall. Deftly Rolf nested the spinners again in their pack before he set out toward the heaped-up mass of stone blocks that was the wall.
 They feared the Ancients.
 They had lost too many to continue fighting.  They were warned not to by Altha.  They feared the Ancients.  They knew they were losing the battle.