Born in Santa María de Meruelo near Santander, Cantabria, Sáinz, whose mother was German, lived in New York City from 1912 to 1922, returned to Spain when his father was stricken by encephalitis, and then obtained an Electric Engineering Degree in Germany with Siemens.1924-26[1] In 1932, while working as the Director of the Office of Tourism in Toledo, he became one of the founding members of the Falange with José Antonio Primo de Rivera.
[2] In the run-up to the war he was a central figure in arranging co-operation between the Falange and the army and he suggested that a proposed coup should begin in Toledo where he was provincial chief.
[2] He was arrested again on June 5 when he was discovered Alcañiz prison, relaying the orders of General Emilio Mola that the coup was to be postponed.
[1] During much of the remainder of the war he organized men and materials, oversaw construction of facilities, and arranged relief for recaptured territories.
After the end of the war Sáinz started a branch of the called Educacion y Descanso, (Work, Education, and Rest),under auspices of The Ministry of the Interior, led by Serrano Suner, overseeing the construction of facilities and policy.
[7] In 1948 a cache of 30 buried pistols captured during the war was discovered on his Cantabrian farm, one of which was used in a robbery, and a warrant was issued by the government for sedition.