I didn't specify, just saying that there were no tanks in the Civil War re enactments that I take part in.
As far as horses making 1.5 HP it is very possible. I mean we all know horses have power-bands, like any engine. You know how when you ride a horse and when you squeeze your boots into it and it goes from a trot to a canter to a sprint and you feel the increase in torque, they called that the "boots" but somewhere along the line it was misread as "boost", so the term boost that we all know so well actually comes from the good old days when we all used horses to get around.
Anyway, back to the HP discussion. Unlike today, when you had your horse dynoed (attached to a rope which went through a sheave 90 degrees to a load hanging vertical) they used an average power figure as opposed to a peak power figure we use today. So to say a horse has 1 HP is just an average figure, in fact many horses had anywhere up to 1.8HP peak power.