Hi Brian! Thanks for the question.
For both Govt Assault and Insurgent Attack, the executing Faction may choose to target one or several Factions, and may target some Factions but not others. If the targeted Faction or Factions have enough pieces, then the amount of pieces that can be removed must be removed.
Here are the relevant rules from the current version of the rulebook:
1.4.1 Availability and Removal, 3rd bullet.
• Once an enemy Faction is targeted, removal of pieces to the extent of the executing Faction’s ability is required. EXAMPLE: A Government Assault (3.2.4) with 3 Troops in Forest must remove 3 Active pieces if there are at least that many among those Factions targeted.
3.1 Operations in General, bullet.
• The executing Faction chooses the order of the spaces in which the Operation is resolved, the enemy Factions or pieces to be affected (targeted), and the friendly pieces to be placed or replaced. A single Operation may target one or more Factions and ignore others.
PROCEDURE: In each selected space, remove 1 Active Guerrilla (1.4.3) for each Troops cube there. Once a targeted Faction has no Guerrillas in the space, remove its Bases instead.
PROCEDURE: In each selected space, Activate (1.4.3) all the executing Faction’s Guerrillas and then roll a die: if the roll is less than or equal to the number of the executing Faction’s Guerrillas there (whether or not they began Active), remove up to 2 enemy pieces (executing Faction’s choice; may include Underground Guerrillas). The 2 pieces may belong to different Factions. A targeted Faction’s Bases cannot be removed before all its cubes or Guerrillas in the space.
Does that answer? Thanks again! - vfr