|Battle of Castillon (source)|
Fighters (but no other class) may also use attack ranks defensively in a similar way to improve their AC from round to round. In addition, fighters may spend their attack ranks to improve the AC of companions they are defending if that makes sense situationally. For example, consider a first level fighter wearing medium armor, using a shield, and fighting near an unarmored magic-user. This fighter has AC 4, the magic-user has AC 9. The fighter has the following options:
- Fight at attack rank 2. All armor classes remain unmodified.
- Fight at attack rank 1 and improve her own armor category one step (AC 2).
- Fight at attack rank 1 and improve the magic-user's armor category one step (AC 7).
- Fight at attack rank 0 and improve the magic-user's armor category two steps (AC 5).
This ability is similar to the defense trait from the Hexagram path of arms. I think it is a nice addition to the fighter class, giving them some ability to defend other characters mechanically without resorting to other cumbersome subsystems. I could also imagine attack ranks potentially being usable for other things too, though I don't want to overload the system too much.