Leslie A. Donovan, in "A Companion to J.R.R. Tolkien", compares the siege of Gondor with the alliance of Elves and Men in their fight against Morgoth and other co-operative ventures in "The Silmarillion", making the point that none of these would have succeeded without collaboration; further that one such success comes from another shared effort, as when the Rohirrim were only able to come to the aid of Gondor because of the joint efforts of Legolas, Gimli, and Aragorn; and that they in turn collaborated with the oathbreakers from the Paths of the Dead.