This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book is concerned with the emergence of a free wage-labour force in a range of low-income countries. For capital to be accumulated a labour force must be created in order that the process of surplus extraction may occur. In many cases labour shortage dictated a process of partial proletarianisation based on migrant labour. Labour supply conditions could be drastically different from one case to the next, and the process of proletarianisation was one of accommodating the level of labour scarcity. The floating surplus population is fully proletarianised and 'free' labour, existing in the industrial centres. Under the enganche system, traders or contractors would most commonly forward loans to individuals who then had to pay these off through the sale of their labour power.