Marx's story of primitive accumulation is best seen as a "special" case of the "general" principle of capitalist market expansion. In part, trade grows incrementally, but usually the establishment of capitalist relations of production involves force and violence; transforming property relations means that assets previously owned by some people are no longer owned by them, but by other people, and making people part with their assets in this way involves coercion. This is an ongoing process of expropriation, Proletarianization and Urbanization.