User blog comment:Zathronas/Speculative author: recap of Volume 2 part 2/@comment-9090085-20140929050631/@comment-10390252-20140929131728

Here's a possibility:

Qrow's motivation is simple enough; Cinder's sponsors (who, I believe, are the anti-Individualism group who were the losing side of the Great War) were responsible for Summer's death and the disappearance of Yang's mother, Qrow's twin sister. He wants vengeance for both of the women in the team. Taiyang's departure from Patch is due to Qrow notifying him that a significant clue is to be found in the White Fang base to the south-east of Vale.

My feeling is that Oobleck and RWBY will arrive just as Qrow and Taiyang make their move, tearing into the base like two men possessed... because they are, in a way. Naturally, the two men stir up a hornet's nest and the WF decide to make their move against Vale now. So, there is a significant number of Mechs plus a huge number of Grimm, all headed for Vale attracted by the concentration of humans and sensing the failure of Vale's perimeter defences (more sabotage by Roman and Cinder's agents).

All attempts to warn Vale fail and it is also impossible to contact the other Kingdoms; the CCT system is off-line for some reason. Taiyang decides that RWBY need to head back to the city to carry the warning back themselves. He, Qrow and Oobleck will attempt a running defence to whittle down the numbers of Grimm and disorganise the White Fang troops.

Naturally, Yang and Ruby wish to stay behind to fight with their kinsmen but Oobleck makes it a direct order. Reluctantly, Ruby acknowledges that he, Blake and Weiss are correct. We last see the three Huntsmen charging towards a near-solid line of Grimm before Ruby, her face streaked with tears, leads her team in a full retreat.