By the early 1930s, Masseria's main rival was boss Salvatore Maranzano, who had come from Sicily to run the Castellammarese clan. Their rivalry eventually escalated into the bloody Castellammarese War. Masseria and Maranzano were so-called "Mustache Petes": older, traditional Mafia bosses who had started their criminal careers in Italy. They believed in upholding the supposed "Old World Mafia" principles of "honor," "tradition," "respect," and "dignity." These bosses refused to work with non-Italians, and were skeptical of working with non-Sicilians. Some of the most conservative bosses worked with only those men with roots in their own Sicilian village.