He framed expropriation as a necessary national response to the injustice of the operations of foreign companies operating on Mexican soil. Expropriation was not outright confiscation since the Mexican government promised to compensate companies. However, in retaliation, many foreign governments closed their markets to Mexican oil until the Allied demand for petroleum in World War II caused the boycott to be dropped. In spite of the early boycott, Pemex developed into one of the largest oil companies in the world and helped Mexico become the fifth-largest oil exporter in the world.