Tortoises are even slower than phalanxes, moving at a speed of 4. A tortoise formation may revert to a more conventional phalanx at any time - this is typically done just before the unit enters melee. Skirmishers Skirmishers are spread out. This formation is comparatively weak - skirmishers gain no combat bonuses. Skirmishers are fast, though, and less vulnerable to missiles and magic than tightly packed pikemen and phalanxes.
Skirmishers move at full speed.
Reforming skirmishers into a tightly controlled unit for melee is difficult, requiring a d20 roll under the number of weeks trained. A tactic used by some nations is the concept of skirmishers armed with crossbows, or in the Savage Coast, arquebuses. Skirmishers armed with such weapons use the tactic now time honoured in the real world - advancing by squads. One unit rushed forward a short distance, a few tens of yards, while another unit hangs back and provides cover with their weapons. Then the first unit that advanced holds and covers, while the previously stationary unit rushes forward, and so on.