Roman Military Structure
Bulgakov researched Roman military structure in the Brokgauz-Efron encyclopedia.
Bulgakov uses the unusual transcription "kenturiia" and "kenturion" (instead of "tsenturiia" and "tsenturion") to defamiliarize the terms.
1 ala = 20 turmae of 15-30 men each.
The ala was a detachment of 300-600 men, usually named for the nationality they were recruited from.