Recruitment from amongst Roman citizens had become greatly curtailed as a consequence of a declining population,* Cary & Scullard, "A History of Rome", p. 537</ref> "cripplingly numerous" categories of those exempted from military service and the spread of Christianity with its pacifist message.* Grant, A History of Rome, p. 333* Santosuosso, "Storming the Heavens", p. 229</ref> Together, these factors culminated in "the withdrawal of the urban class from all forms of military activity." In their place, much of Rome's military were now recruited from non-Italian peoples living within the empire's borders. Many of these people were barbarians or semi-barbarians recently settled from lands beyond the empire, including several colonies of "Carpi", "Bastarnae" and "Sarmatians".