Dynasty Warriors 5:XL - Legend of Dian Wei 6 - Escape from Chi Bi

This is a retreating battle where you're escorting Cao Cao. The faster you defeat enemies the faster the way clears, however if you don't defeat them fast enough reinforcements will appear and tell Cao Cao to go on while they take care of it and he'll start moving. It's best to defeat the officers to keep your allies freed up for when Sun Quan appears and his forces move after you, so they can work to hold him off while you continue making the escape past the Shu forces.