Columbia subject headings:
Harvard subject headings:
Islamic Empire--History, Military.
Military ethics.
Peace--Religious aspects--Islam
War--Religious aspects--Islam
ʻUmar ibn al-Khaṭṭāb, Caliph, -644--Military leadership.
Princeton subject headings:
Islamic Empire--History--622-661.
Military ethics--Religious aspects--Islam.
War--Religious aspects--Islam.
ʻUmar ibn al-Khaṭṭāb, Caliph, -644.