Board Thread:Questions and Answers/@comment-24463723-20140205192108/@comment-6007020-20140205224718

Since Shunsui and Ukitake destroyed the Sokyoku with a device that belonged to Yoruichi Shihōin's clan, it wouldn't be a stretch to believe she helped them get ahold of the device. Yoruichi most likely wouldn't have even bothered with saving Rukia if Ichigo hadn't planned on going. Without the Shield, Ukitake and Shunsui would've have resorted to an all-out attack against the ceremony, which more likely than not would have resulted in their deaths.

On the subject of Aizen, do remember than you only need to witness him release his Shikai once and your five sense are under his complete control. Starting a big commotion would have been child's play, and the only thing that stopped him was Ichigo's arrival, who did Aizen's work for him. Would you bother doing something if someone already did a good enough job of it for you?

Also, Squad 4 is the medical division, not Squad 3.