Spartans and Orcs
The 300 Spartans face off against the infantry and cavalry part of the army that attacked Minas Tirith. They know they are on a suicide mission, but if they do not fight the orcs then they know Sparta will burn and Greece will fall. All 300 are there, with another 200 greek warriors of almost-equal skill level (they stil have to be elites, right =-p)
There are no Nazgul, no Mumakil, and no other wordly things, straight orcs and guys on horses. The Eye cant see them. Battle takes place starting with a phalanx at the main gates of Minas Tirith. Reinforcements are 2 weeks off. How long do the spartans hold out?