When an attack is made against you, your opponent must first make a successful attack. If he misses, he misses, and the attack ends. If his attack succeeds, the combat system rolls against your defense. If your defense fails, the attack succeeds, and damage (possibly reduced or negated entirely by armor) is applied. If your defense succeeds, the amount by which you made your defense roll is compared to the amount by which your opponent made his attack roll. If you made your roll by more, you avoid the attack. If your opponent made his roll by more, the attack succeeds.

Your defense is determined by your defense mode. There are three defense modes: Dodge, Block, and Parry. Most defense modes work against most weapons... but not all: the defense modes that are effective against a specific weapon are specified when the weapon is +defined. In general, with the default weapons supplied with a base distribution of Argo, you can use any defense mode against any weapon with the following exception: many ranged weapons, such as Bows and Crossbows, cannot be parried. On high tech worlds, Dodge will also usually be ineffective against ranged weapons.

+dodge sets your defense mode to Dodge: you attempt to avoid attacks by moving out of their way. Your Dodge skill is equal to your current STR + current DEX divided by 2 plus 2. You may declare +dodge at any time. Dodging is the only defense mode available if you have no shield or weapon that can parry. It may also be your best choice if you are unskilled with your weapon or shield.

+block sets your defense mode to Block: you attempt to avoid attacks by warding them off with your shield. You must have a readied shield in order to block. Your Block skill is equal to your current Physical skill plus your Shield skill.

+parry sets your defense mode to Parry: you attempt to avoid attacks by deflecting them with your weapon. You must have a readied weapon in order to parry. Your Parry skill is equal to your current Physical Ability plus your weapon skill minus 1. Players who have the fencing skill and are using fencing weapons receive an additional bonus when parrying (see Fencing). Not all weapons may be used to parry.

+nodef `turns off' your defenses: you have no defense mode set. When you have no defense mode, you are concentrating entirely on your attack: rolls to hit are made at +2.