Combat is one of the most important and most complex aspects of the D&D game. Designers want to keep things simple and clean while players constantly strive to push the envelope and stretch the boundaries of both what's allowed and what's possible. In D&D 3.5, the designers have pulled off a real-life feat of their own in the way they're streamlining the combat chapter and making the rules easier to understand.
Q: How have attacks of opportunity changed?
A: They haven't, really, but the rules have been clarified. Attacks of opportunity are an important balancing factor in the game. Too many people weren't using them, unfortunately, mainly because they didn't understand how attacks of opportunity worked. That section of the rules was rewritten to make it easier to understand and implement for both players and DMs.
Q: Eliminating partial actions will help clean up the system. Are any other changes being considered for the action categories?
A: Similar to attacks of opportunity, the "changes" are mostly clarifications. The new text is easier to understand. We're really proud of the fact that the revised combat chapter is both clearer and shorter than before without really taking anything away from the players. When you start working on combat rules, you're trying to reduce some pretty complex activity into just a few relatively simple options. With 3.0, we were happy with the combat rules and actions as they played -- the difficulty was explaining them in a way that let everyone grasp our intent and implement the rules the same way whether you're playing with Ph.D.s at NASA or with 12-year-olds in the middle school lunch hall. With the rewrite, we focused on laying out the basic system in clear, unambiguous language. We eliminated redundancies and stuck rigorously to the fundamentals. For example, you won't find any discussion of charging, grappling, turning undead, or other heroic or fantastic actions in the generalized discussion of combat. We want people to focus completely on understanding the basics before we start layering on all the "special actions" that make this fantasy combat. The special actions are still there but in their own section, so it's easier to see how they add onto the basic system without disrupting it. The end result is combat rules that are tighter, cleaner, and easier to grasp than any we've done before. After reading this chapter, determining whether something is a standard action, a move action, a full-round action, a free action, a restricted activity, or not an action at all should be simple and intuitive.
Q: Which feats have been changed?
A: Most of them remain the same, with only some clarifications. A few are being changed to improve balance. The most noticeable difference will be that quite a few feats were renamed for reasons of internal logic. The feat Sunder, for example, is being renamed Improved Sunder, and sunder is now a combat action. We determined (based on feedback!) that there was no real reason a character without the Sunder feat couldn't break a weapon, and players wanted to try. Actually doing it is a lot easier if you have the feat, plus then you don't draw an attack of opportunity.
Q: Are there any other tidbits about combat that you're willing to share?
A: The Dungeon Master's Guide is going to cover some conditions and environments that weren't dealt with in the original 3.0 books. Underwater combat, for example, gets a nifty little section of its own, complete with an illustration.