 Guerrilla warfare can be considered progressive if  only enemy combatants are targeted but becomes terrorism when non-combatants are targeted.
<clarity>  Guerrilla warfare can be considered progressive if  only enemy combatants are targeted but becomes terrorism when non-combatants are targeted.
 Guerrilla warfare can be considered progressive if only enemy combatants that are targeted, but it becomes terrorism when non-combatants are targeted.