Friedrich Ratzel's Organic Theory of the State

Friedrich Ratzel's Organic Theory of the State (late 1800s) compares a state to a living organism. According to the theory, a state needs territory ("Lebensraum") to grow and survive, just like an organism needs food and space. Expansion is seen as a natural and necessary process. Though originally academic, this idea later influenced nationalist and imperialist ideologies, especially Nazi Germany.