The entire French West Africa-Saguia el Hamara/Rio de Oro boundary was confirmed by treaty on 19 December 1956, with France and Spain then demarcating it on the ground in 1957 with several pillars. From 1946-58 Spanish Morocco, the Tarfaya Strip, Ifni, Rio de Oro and Saguia el Hamra were united as Spanish West Africa. Morocco gained independence from France in 1956, including Spanish Morocco (minus the plazas de soberanía which remain part of Spain today). The newly independent state, inspired by the idea of creating a 'Greater Morocco', claimed all of Spanish West Africa as Moroccan land. In 1958 Spain merged Rio de Oro and Saguia el-Hamara in 1958 as Spanish Sahara; that same year Spain ceded the Tarfaya Strip to Morocco (via the Treaty of Angra de Cintra). Ifni was ceded in 1969 (following a failed Moroccan attempt to capture the region by force in 1957). Morocco then turned its sights to Spanish Sahara, however Mauritania (independent since 1960) also contested the territory, claiming the former colony of Rio de Oro as part of 'Greater Mauritania'. A railway was built in 1960-63 which paralleled the southern half of the boundary, including an expensive tunnel through an escapement north-west of Choum constructed so as to order to avoid the right-angle of the south-eastern Spanish Sahara. Saharawi nationalists had meanwhile formed the Polisario, seeking independence for the whole of Spanish Sahara as Western Sahara, and began a low-level guerrilla campaign. An International Court of Justice ruling on the matter in October 1975 stated that neither the Moroccan nor Mauritanian claims to Western Sahara were strong enough to justify annexation, and that the Saharawi people should be allowed to determine their own future. Morocco thereafter sought to settle the matter military, and in November 1975 conducted the 'Green March', in which thousands of soldiers and Moroccan nationalists forcibly crossed the Morocco-Spanish Sahara border. Spain's dictator Francisco Franco was at this time near-death, and the country was unwilling to respond militarily at such a delicate time, keen to avoid the kind of drawn-out colonial war that had bedevilled Portugal in its African colonies. Spain therefore signed a treaty with Morocco and Mauritania, splitting Spanish Sahara roughly in two, roughly two-thirds in Morocco's favour. By this treaty only the northern third of the traditional Mauritania–Western Sahara border remained extant.