Board Thread:Questions and Answers/@comment-7708862-20130402005255/@comment-2182964-20130403170207

There are plenty of plot-holes, true, but Ulquiorra says that the top 4 Espada where not allowed to release their Zanpakuto within Las Noches. As he counted himself amongst that number, the scale obviously goes 4 - Ulquiorra, 3 - Halibel, 2 - Barragan, and finally 1 - Stark. SunXia is right in this case: it was never said they'd destroy the fortress outright (as in it goes "boom"): merely that the release could cause potential damage to their base that was better avoided.