Combat NPCs areolding anything it will pick up any item thrown at it.
Whenever in range of a hostile mob a Combat NPC will start attacking it. A Combat NPC will also attack any mob the player is hurt by or attacked by similar to a wolf.
Below is a table containing the Combat NPC's professions
Soldiers are trained by giving an NPC a sword. They will rush at the enemy attacking with their sword. Their damage is dependent on the attack damage of their sword. Also, they need food.
Archers are trained by giving an NPC a bow. They will remain in one position unless attacked or their target has gone out of range. Archers will deal 3-4 damage with no enchantments (same as a bow drawn half back) and 6-7 damage with Power V.
Medics are trained by giving a Combat NPC an axe. They will rush mobs similar to soldiers but will attack slower with damage being dependent on the attack damage of their axe. If there are no mobs in the area the medic will prioritise healing itself then the nearest NPC for 5HP (2.5 hearts) each heal.
Engineers are trained by giving a Combat NPC a Hammer. They will rush mobs similar to soldiers but will have a slower attack. Their damage is dependent on their attack damage of their hammer.
Commanders are trained by giving a Combat NPC a Command Baton. They will rush mobs like soldiers but will provide a strength buff to all Combat NPCs in range while fighting. Their damage is dependent on the attack damage of their baton.