In explaining the process of frontier expansion, the emphasis has rightly been placed on spontaneous migration to the frontier, rather than on planned colonisation of the frontier. The pioneering movement is primarily determined, as was argued in Chapter 3, by the ‘surplus’ of labour and monopoly of land in the countryside, and by the rising demand for staple foods in the cities. Planned colonisation appears to have contributed little to the movement, not because plans for colonisation were lacking, but because most such plans, both public and private, met with failure. Public planning of colonisation has recurred throughout the period of the pioneer frontier, with occasional concerted efforts to direct the pioneering movement, such as the series of incentives to colonisation provided by Vargas under the Estado Novo, which were heralded collectively as ‘The March to the West’ (Esterci 1972). But of the tens of national colonies inaugurated in the years following the collation of this legislation in 1945, only one or two managed to survive and prosper (Diegues 1959), which is indicative of the small success of public colonisation initiatives over the period. Such public policies necessarily obeyed political imperatives, such as ‘peopling the political boundaries of the nation’, and therefore the collapse of most of the colonies may be explained by a lack of any economic viability. But private colonisation plans, which in principle should respond to clear economic incentives, appear to have met a similar fate.