Nope, your forces will attack goblins by default but the yetti are
effectively off the map and to attack them you actually need to send your
forces out on a raid, check which key in the readme, (It could've been ctrl
enter but as I said I've not played the game for quite some time). I forget
Hi Ari.
guard towers aren't as much a priority and won't help you against the yetti,
just against the goblins.
The way your military forces work is that they'll leave your barracks and
attack the closest lot of goblins, then after each attack, return to the
barracks before going out again.