A War of Attrition was an altered representation of one of Aguilar de Nerha's genetic memories.
Aguilar's Journal
We succeeded in preventing the Templars from acquiring the second piece of the Staff of Eden. It is now hidden in a safe location. However, Torquemada has escalated his aggression, sending the Spanish Army directly to bear on the province of Granada and its Sultan Muhammad XII. Torquemada has learned that the Sultan hides the true location of the Apple of Eden.
Spain's army currently prepares to lay siege to Fort Baza. We must make this a battle of attrition and fortitude. Our plan is to deprive the Spanish army of its food and supplies to weaken their offensive.
Outcome
The Assassins destroyed the supplies, preventing the Templars from restocking consumed food or repairing used war matériel.