I was surprised a few days ago to find myself in an argument with a reputable historian about the Romans' use of dogs in war, which I dismissed as a fantasy — or possibly a mere misunderstanding of Antony's soliloquy in (Shakespeare's) 'Julius Caesar', where he says Cry Havoc! and let slip the dogs of war.
The only genuine/original reference that I can find is in Vegetius IV.27, where he describes the use of guard dogs, trained to bark at the surreptitious approach of an enemy. Other internet searches have turned up nothing but simple assertions that dogs were trained for, and used, in war, and there are even illustrations — but no actual evidence. I already knew about the canis molossus, a kind of mastiff which is surely historical, but no reference that I can trace suggests its use in warfare.
The whole thing seems unlikely, but perhaps I am wrong to reject it. Is there anywhere a source in support of the Romans' use of dogs in war?