A Turncoat, also known as a Turncloak, is a person who shifts allegiance from one loyalty or ideal to another, betraying or deserting an original cause by switching to the opposing side or party.
In political and social history, this is distinct from being a traitor, as the switch mostly takes place under the following circumstances: From a military perspective, opposing armies generally wear uniforms of contrasting colors to prevent incidents of friendly fire.
One example would be the situation that led to the Act of Abjuration or Plakkaat van Verlatinghe, signed on July 26, 1581, in the Netherlands, an instance where changing sides was given a positive meaning.
A mass-shift in allegiance by a population may take place during military occupation, after a nation has been defeated in war or after a major social upheaval, such as a revolution.
This is especially apparent in dictatorships and authoritarian states when most of the population has been fed propaganda and triumphalism and has been kept in the dark about important turns of events.