When two opponents share dislike for a third enemy, they might be more inclined to fight together against their shared enemy than against each other. Propagandists sometimes exploit shared hatreds or fears by suggesting a common enemy that might have no relevance to a conflict. The Common enemy, used usually to denote a foreign organization, group, or league, is designated by a party (mostly governments) and includes members of the opposition to that party (and, sometimes, another party).
By attributing problems to an idealized common enemy, propagandists can arouse emotion among diverse groups and they can divert attention from the causes of real problems. Adolph Hitler's rhetoric targeted among others people of Jewish descent, rousing emotion that drove Hitler's rise to power and providing an easy albeit irrational answer for complex socio-economic problems.
Two parties can sometimes set aside differences when faced with a shared threat. U.S. President Ronald Reagan suggested that people of Earth during the Cold War era would set aside their differences if confronted by an invader from another planet. Though his comment alone may have had little to do with the end of that global conflict, Reagan used the idea of a common enemy to create rhetorical unity among enemies.
In the United States, the war on drugs has targeted users of illegal drugs as a common enemy. Critics allege attention toward those who self-medicate diverts attention from widespread psychological distress and from dangerous or unhealthy conditions in workplaces and schools.