You may set Leonardo's formidable intellect to each of the following problems:

• Artillery Accuracy: Leonardo inspects one war machine in the army and observes some test shots. He then calculates angles and trajectories and makes corrections to the devices or advises on firing technique, quantity of gunpowder, torque tension and so forth, which increases the accuracy and reliability.
  As long as Leonardo is within 3" of one war machine, that war machine may re-roll one Artillery Dice, Scatter Dice, or To Hit roll per turn.

• Crossbow Accuracy: Leonardo inspects one unit of Crossbowmen as they shoot volleys at targets. He checks the tension of the bows and considers wind velocity and the weight of the crossbow bolts. He may advise certain subtle reshaping of the flights to improve accuracy, or recommend that the crossbowmen aim slightly to the left or right of their target, or just above their heads.
  As long as Leonardo is with a unit armed with crossbows, the unit may re-roll all failed rolls of 1 To Hit in the Shooting phase.

• Battle Strategy: Leonardo inspects the maps and charts and rides up to high ground to survey the lie of the land with his telescope. Then he discusses the options with the general and his captains in a council of war, explaining his calculations for rates of march and so on. This enables the general to outflank the opposing army.
  One Core unit in the army gains the Ambushers special rule.