https://en.wikipedia.org/wiki/Anti-tank_dog
It's a good thing that horses have been superseded. Animals should not be pulled into our wars.
If so, it’s usually considered ethically acceptable.
See: land mines, white phosphorus, etc.
Chemical and biological weapons are in the few exceptions, and that is generally because they are very difficult to control and use without hurting your own troops as much or more.
There is a joke about intelligent apes like orangutans and chimpanzees: they could probably learn to speak, but they refuse to do so out of fear that people would try to employ them.
https://en.wikipedia.org/wiki/The_Day_of_the_Dolphin
though admittedly in the fiction the dolphins were trained to place the explosives and leave.
About the supposed use of dolphins in Sevastopol:
https://www.livescience.com/russians-using-military-dolphins...
they seem like a marine version of the good ol' Roman geese:
https://en.wikipedia.org/wiki/Brennus_(leader_of_the_Senones...
a sort of intrusion alarm.