On one side of the Castellamarese War were the Castellamarese and every boss allied with them.

On the other side was everyone else allied to Joe the Boss. Therefore it is simply a matter of deciding which bosses existed at the time and who were they allied with, Maranzano or Masseria, to determine who was a "Capo" in the Masseria organization. What is a boss today was a lieutenant then, under the boss of bosses.

I think Masseria had his own gang, and then other gangs were allied to him and paid him tribute, such as Al Capone's.

Another kind of Capo Masseria had were the captains/group leaders within his own family. To discover that, someone has to do something very interesting. They need to construct a chart of the old Luciano Family.

Clearly Vito is there. Clearly Costello is there. Clearly Adonis is there.

If the old Corleonesi Clan that lived up in Harlem, the Morellos, were absorbed into Joe the Boss' organization, then you assign a principal to them and then you have another possible Captain in the Masseria organization. Peter Morello? Yes, Bigtime. He was definitely a group leader or leading figure behind Masseria. After he was assassinated, one of the Morello brothers probably took his place and that brother became another of Masseria's chief lietenants or capos if you will.

On a side note, I don't think Lucky Luciano ever held a position in the mafia lower than capo. I think he and his bootlegging operation were absorbed directly into Masseria's conglomerate where Charlie sort of became Masseria's driver, bodyguard, and assistant. Some would say maybe he wasn't Underboss, that Peter Morello was the closest thing to an Underboss in the Masseria mob. But that's why we're here, to find out. Did Underboss even exist at that time, or was it just the most prominent captain in a gang under the Boss? The Castellamarese weren't into bosses and gangs and mobs, but rather family and father. There was no "underfather" in the prehistoric Bonanno Clan. There was just the father.