DYNASTY WARRIORS 6

Scenario: Battle of He Fei
Side: Wu forces
Complete Target 1, "Kill Cao Ren and Xu Zhu in 10 minutes".

I would recommend taking out Cao Ren first, and capturing the West Castle. From there, make your way to Xu Zhu's location in the middle of the map.

By the time you've taken him out, enemy reinforcements should have arrived in the NW corner of the map. Return to the West Castle and mop them up.

From there, head to the East Castle and take it to end the level.

I had impatiently attempted rushing this a couple of times and failed, either from allied generals killing one of them (which auto-fails the target for you), or from enemy generals killing my allied leader, ending in a loss. In the end, I took the more methodical approach, outlined above. This worked on my first try.

If you can't do this in any Musuo modes, be aware that you can always go back and get it in free play with a leveled character.

The actual achievement does not unlock until you have saved your game.