Not necessarily.
Unit response seems to be influenced by the opposing creature (size and scent possibly?) Number of closeby friendlies, personality, emotional hardening, and training (represented by the discipline skill.)
Dwarves who like to pick fights, have a sense of duty, and are generally adventurous individuals may outright attack intruders without being part of the militia, and even somewhat cowardly individuals will throw caution to the wind if there's a large number of friendly units nearby; my guess being they may take on a mob mentality and try to swarm the intruder with sheer numbers like ants or something, as I have had children lash out at invading mandrills that climbed over a wall in one fort and even managed to kill two of them (three in all, with four others taking the long way. One kid died, the rest of the mandrills ended up on the business end of several bronze swords and copper maces.)
Personality and training are the biggest ones, as it seems to require roughly 5 discipline to be able to keep fighting with numerous deaths in a battle if they have a tendency towards cowardice. Any lower than that and more than one or two kills will cause them to be overwhelmed by horror (and unable to fight.)
On that note, individuals who have positive personality traits for the military (sense of duty, adventurous, likes to brawl/pick fights with others, and values war over peace) will train as diligently and fight as fiercely (if not as well) as a damned weapon master. On the inverse, it may take considerably more training to get peace-loving dwarves to fight nearly as well, and it's likely that it could be said if they train and fight at all it's because they feel they need to to protect thier home and loved ones, where the former wants to fight just to kick the shit out of any dumb goblin, elf, or what have you that crosses their path.
All recruits however will train themselves to the point of exhaustion at times; I've seen sparring matches between non-weapon masters go on and on until one or both physically couldn't stand up anymore they were going at it so fiercely.
That being said, with the way things are traps will definitely be permitted on a large scale. Having soldiers who may break and run at the first sign of trouble makes that a necessity.