The great ships were hive minds, concatenations of thousands of smaller ships that swarmed together so closely you couldn't tell where one ended and another began. They were supposed to be unstoppable, but they had one vulnerability: internal dissent. If you could talk a few ships into separating from the whole, you had a chance.
The sleek, massive ship would become a disintegrating chaos of smaller ships, each seeking its own counsel.
Emmanuel Shiu is a concept artist who has worked on a number of films. You can see more of his work on his website.