Language policies of Francoist Spain

Language politics in Francoist Spain centered on attempts in Spain under Franco to increase the dominance of the Spanish language (Castilian) over the other languages of Spain. The regime of Francisco Franco had Spanish nationalism as one of its bases.

Under his dictatorship, the Spanish language (known in some parts of Spain as castellano, i.e., Castilian) was declared Spain's only official language. The public use of other languages was either banned, frowned upon or despised depending on the particular circumstances and timing, while the use of non Castilian names for newborns was forbidden in 1938, except for foreigners. The situation evolved from the harshest years of the immediate afterwar (especially the 1940s, also the 1950s) to the relative tolerance of the last years (late 1960s and early 1970s); Franco died in 1975, and his successor Juan Carlos of Spain began the Spanish transition to democracy.

For the first time in the history of Spain, the Second Republic recognised Galician, Basque, and Catalan as official languages when it granted autonomy for some regions with a regional language.

As part of the nationalistic efforts:

In the first decade of Franco's rule, languages other than Castilian were "confined to private spaces".

In the regime's most radical discourse, languages other than Spanish were often considered "dialects" in the sense of speeches that were not developed enough to be "real languages". Basque was different enough that it could not be taken as a debased form of Spanish but was despised as a rural language of limited currency, unfit for modern discourse. This never happened at the academic level, though.

All these policies became less strict and more permissive as time passed.

...
Wikipedia