I have a player wanting to purchase a "war trained" mastiff as a mount (think warhorse) and he is getting this from the MM description:
Mastiffs are impressive hounds prized by humanoids for their loyalty and keen senses. Mastiffs can be trained as guard dogs, hunting dogs, and war dogs. Halflings and other Small humanoids ride them as mounts.
I looked but can't find any description of the benefits or differences of a war dog. Any idea where I can find them?