The amount of people I see calling Erwin an amazing tactician baffles me. Nearly every singe battle plan of his either failed miserably or barely succeeded, and always depleted the ranks.
He showed his incredible incompetence with his attempt at capturing Annie. It failed miserably and killed the majority of the scouts, including all of their most skilled soldiers except for Levi and Miche, who is supposed to be even better then Mikasa but ended up dying the most idiotic and preventable death in the whole series. All they had to do was have Levi and his team rip her out of her titan, Levi even had a plan to do the same with Eren, and bring her back with them.
Instead he places a bunch of harpoon guns around a single area, bets it all on an easily missed shot, wastes dozens of skilled soldiers so they can bait her into the trap, and it all fails because they never counted on the possibility of shifters being able to command mindless titans, which was pretty plausible. Trying to capture her alive in the first place was exceptional anyways, since shifters can form a new titan as long as they have an open wound, even when they have all their limbs cut off.
Or they can't, it depends on whether or not Isayama remembers that Eren was missing an arm and a leg when he first transformed.