When assigning combat damage to multiple opposing units, are you required to assign lethal damage to each unit before moving to the next, or can you split damage freely?

Ruling: Once you start assigning damage to a unit, you must continue assigning damage to that unit until either you have assigned lethal damage to it or you have no more damage left to assign. You cannot freely split damage across multiple units.

Sequence:

• Begin assigning damage to a defending unit
• Continue assigning damage to that same unit until lethal damage is assigned
• Only then can you move to assign damage to another unit
• Repeat until all damage is assigned or all defending units have received lethal damage

Nuances:

• In the example with a 4 power attacker vs four 2 power defenders, you cannot assign 1 damage to each; you must assign 2 damage to the first unit (lethal), then 2 damage to the second unit (lethal)
• Might increase effects (like Darius's buff) stop applying after all units heal from combat damage, so units that survive only due to the buff will die after combat resolves