Board Thread:Theories and Speculation/@comment-31661816-20170403165339/@comment-734582-20170405130606

Tasuxeda wrote: only makes sense to me if only the ANBU that said it could only be broken from the inside wanted to kill the Third Doubt it. The building was in the middle of the village, so any jutsu capable of breaking the barrier would likely be enormously destructive.

Even so, Orochimaru did have a significant information advantage, and had Danzo on his side probably. It wouldn't be hard for him to keep any ANBU capable of breaking the barrier away from the village when the attack happened.