The word "intervention" comes from the Latin word "intervenire" and means "to come between". In international law, which regulates the relations between nations, intervention means an unjustified intrusion into the affairs of another state or into a quarrel between two states. An intervention can then be seen as a hostile act. There have often been interventions throughout the history of international politics. One example is the Spanish Civil War at the end of the 1930s. Several fascist powers, including Germany, supported the Spanish General Franco in his rebellion against the Spanish Republic.
In the past few years, there have been several interventions for humanitarian reasons and to protect human rights. For example, this occurred in Ruanda when soldiers from various countries intervened with the permission of the UN to end a civil war.