I don’t remeber the movies, but didn’t the dead finish the battle around Minas Tirith? In books, they defeated the fleet of bad guys near the mouth of Anduin, freeing significant army, which then takes the ships anf goes to Minas Tirith. The rest of the battle there is not unusually supernatural, if I remember correctly. I remeber not likig this part of the film. I understand it, but I think this part in particular felt very abrupt.