Board Thread:Manga/@comment-26056057-20160509020829/@comment-26932251-20160510211714

93.80.44.40 wrote: I reckon these are just random titans somehow controlled by Zeke. It is still unclear how he controls them. Hold up hold up...

Did you forget when the Survey Corps entered Shiganshina? There's that one panel where suddenly all of the titans just appear in a neat semi-circle around the back end of shiganshina in flashes of lightning. They're not random titans, they were generated at just that moment.