war animals are a wonderful thing, exspecially if they are tough. those things dont need to be the ones ripping everything apart (those are usefull too though) but i prefer tanky ones if i can get a few to breed. normally i would place them in a floodgate trap right at my entrance (accessible from 1 z level above secured with a hatchvover and a drawbridge to seal it off) and release them on any nearing invader, to distract them long enough for my archers to do some damage and my melee dwarfs to get into melee without getting pummeled to death by miullions of bolts/arrows flying my way. (its even better if you place a single row of cage traps just after the floodgates, cause most incaders will stop at the first row until they decide to test out the next row, giving me enough time to open the floodgates if there are no buildign destroyers. also it trains your animal trainer. even if you just want to breed and butcher those dogs of yours, i sugegst to let every single one be trained to war or hunting dogs before you butcher them^^ that might come in handy if you catch a dragon or roc (or two of them of different genders for breeding, if you are that lucky^^) overall i always have some war beast lurking around and assigned to my archers (those tanky ones) and the glass cannon style animals usually in a great number with my melee dwarfs to be targets for enemy fire and possibli to mangle my enemys to bits!