|In Isle of Conquest, destroy 10 vehicles and 100 players with turrets.|
The turrets referred to are the ones on top of the keep towers on the outer walls.
Note that for this achievement, while you gain credit for killing players in the same fashion as for other achievements (participating is enough, you don't need to get the killing blow), you gain credit for vehicles only if your turret scores the kill.
Patches and hotfixes
Patch 3.2.0 (04-Aug-2009): Added