It certainly was at at least one stage in history. Before nation states, a common religion could unify a large army that would otherwise be divided by tribal/e

It certainly was at at least one stage in history. Before nation states, a common religion could unify a large army that would otherwise be divided by tribal/ethnic loyalties. It did for the Byzantine army after Constantine's conversion, and worked spectacularly well a few hundred years later for the armies of the Caliphs.