Tactics
Defaults: IQ-6, Strategy (any)-6.
This is the ability to outguess and outmaneuver the enemy in small-unit or personal combat. In most settings, only the military teaches this skill.
When commanding a small unit, roll against Tactics to place your troops correctly for an ambush, know where to post sentries, etc. At the GM’s option, a successful roll might even provide clues as to immediate enemy plans. To outmaneuver enemy units, you must win a Quick Contest of Tactics with their leader. All of this only applies when you lead a group small enough that you can give each warrior orders personally – or through at most one subordinate. Thus, radio and similar technologies can greatly enhance your command abilities!
In personal combat, you may make a Tactics roll before the fight begins if you had any time to prepare. On a success, you start the fight in an advantageous position – e.g., behind cover or on higher ground – as determined by the GM. The better the roll, the greater your advantage. If you fail, or do not attempt a Tactics roll, you are in a random location (or one of the GM's choosing) when combat begins. Fighters without Tactics skill always start combat this way.
Even in an ambush or similar "surprise" situation, the GM will use the better of your Tactics skill and your Perception to see if you spotted the danger on time.
Martial Arts
Tactics is a martial-arts skill, but it works before the action starts. Below are two options for the GM to use in place of the above rules.
Abstract: If not using a map, roll a Quick Contest of Tactics between the leaders of the two sides before the battle. The winner receives "rerolls" equal to his margin of victory. If his side has 10+ fighters, multiply this by 10% of the size of his force and round down; e.g., for 15 warriors, victory by four gives six rerolls.
In battle, a leader may grant his rerolls to any ally who has just attempted a combat-related die roll. The recipient rolls twice more and selects the best result. The leader's player must describe how such tactical factors as cover and formation altered the outcome. If the GM disagrees, the reroll is wasted. Unused rerolls disappear at the end of the fight.
Mapped: This method is intended for tactical combat in which the plot doesn't dictate force placement. The GM must first designate what part of the battlefield each side controls when hostilities begin. It's fairest to bisect the map – north/south, left/right, etc. – unless the story demands otherwise. In player vs. player conflict, any division that both sides agree on is acceptable.
Next, roll a Quick Contest of Tactics between the leaders, recording the margin of victory. The winner chooses whether he or his rival puts warriors on the map first. In a tie, flip a coin or roll a die. The leaders then take turns placing one man – or 10% of their forces, if larger – on their side of the map.
Once everyone is on the map, the winner may move one ally (or 10% of his men, if larger) to a more favorable position on the "friendly" side of the map or one opponent (or 10% of the enemy, if larger) into adverse circumstances on the "hostile" side per point of victory. He may move fighters toward or away from bad footing, cover, concealment, support, etc. He may not move his warriors behind the foe or turn enemies to face the wrong way.