Why did Marley only bring 500 soldiers to attack shinganshina?

I get that in the liberio attack, they lost most of their forces, fleets and chain of command but they still should've had atleast a substantial amount. I mean they were doing the most important operation in history by capturing Eren, the Founding titan once and for all. I think they should've brought more. Maybe just 1500 soldiers ATLEAST. In "the warhammer titan" episode, Magath called down an entire division doing training in the mountains, and im sure they could've had a few more conscripts in reserve that weren't decimated in the liberio assault.