Tactics

Tactics is the skill to create a battle plan, to adjust that plan when it becomes a fatality at the first enemy contact and generally a very useful skill in battle – or before battle is joined. This skill does not only encompass tactics, but also the big brother of tactics: strategy.
Bonuses can be given for familiarity with the battle field (it's easiest to fight in your own neighborhood) or even, if there is still time, by consulting a book like Sun Tzu's “the art of war”. Handicaps for lack of time to prepare, lack of familiarity with local conditions etc.

The starting value is: 5 + P + I + 2 * Co