Where the tail is, is an important part in communication with other dogs AND humans. The differences in the types of wag determine the different emotions the dog is displaying. Usually when a dog sees a piece of food it wants or likes, it is usually a much less fast, ecstatic wag than it would be if, say, you came home after being out all day.
Also, especially water dogs, they use it as a rudder when they're in the water to stay afloat and helps guide them.
But no, D-S, a slow wagging tail means that they're on guard. When the tail is hanging horizontal, but not stiff, is when they're more interested or curious.
War is an extension of economics and diplomacy through other means.
Economics and diplomacy are methods of securing resources used by humans.
Securing resources is the one necessary behavior for all living things.
War = Life