A dog submits when it accepts the superiority of another being. It is crucial to differentiate submissiveness over fear. Fear causes the act of retreat while submissive dog approaches – very often with joy – another dog with greater dominance because it wants the best one to be a leader.
There are different ways to show the submission. Some are less while other are more expressed. Typical posture is lowered ears, low-set head and body while tail is neutral or lower than neutral positioned depending on the level of submission. It can be accompanied by wide tail-wag and sometimes even with short peeing or cub-like impersonations – such as begging for food.
Absolute submissiveness is demonstrated when a dog lays on its back.
If it feels threatened but is not ready for a conflict, or it just engaged in a fight but it gets injuries that feel threatening or cause pain, fear... a dog will switch from one behavioural act to another: from conflict to submission or flight.