In November 1973 Frei wrote a historic letter to Mariano Rumor, President of the International Christian Democrats, endorsing the Armed Forces intervention and denouncing what he alleged was an attempt by Allende to impose a Communist dictatorship in Chile.
Pada November 1973 Frei menulis surat yang bersejarah kepada Mariano Rumor, Presiden Kristen Demokrat Internasional, yang isinya mendukung intervensi Angkatan Bersenjata dan mengecam usaha Allende untuk memaksakan suatu diktatur komunis di Chili.