President Carlos Lleras Restrepo in Colombia gave a boost to economic policy called Import Substitution Industrialization (ISI) during his tenure (1966-70). The strong Keynesian content was not an isolated event in Latin America, where it extended its use from the 1950s in response to delays and applying the current global economic paradigm. The results would have no parallel in the twentieth century. These facts are analyzed in three sections: 1) characteristics of the Golden Age of Capitalism, 2) development theories then in vogue, 3) the war in Latin America. Finally a brief conclusion.