A Surprise Attack occurs whenever one side is caught off guard and unprepared to enter combat - the GM determines which players or monsters fall into this category. This situation might occur when a trap has been laid or simply in an unexpected circumstance, such a player wandering away from the group and stumbling into a pack of monsters.
Determining need for Surprise Attack Round:
A Surprise Attack Round begins by requiring those characters or monsters who are about to be Surprised Attacked AND who may be able to anticipate this attack to each make a Perception Check. The results of this Check determine what can be done in the Surprise Attack Round.
A typical example would be a group of adventurers walk into a room where a group of bandits are waiting for them, arrows and swords at the ready. The adventuring party is caught off guard, and in this case, only the members in the front of the party might be able to react fast enough to counter the attacking bandits. Thus, they would get to make a Perception Check, while the poor fools in the back of the party are caught completely by surprise. The bandits are not surprised and effectively all make their Perception Checks.
This rule should give people a reason to utilize ambushes and reward an approach to combat aside from brute force. The guy with the huge axe is not necessarily the most powerful if somebody puts a few bullets in him when he’s caught off guard!