He is described as "the rouser of armies" because he rallied the Trojan army when they were falling apart.
hiː ɪz dᵻskɹˈaɪbd æz "ðə ɹˈaʊsɚɹ ʌv ˈɑːɹmiz" bɪkˈʌz hiː ɹˈælid ðə tɹˈoʊdʒən ˈɑːɹmi wɛn ðeɪ wɜː fˈɔːlɪŋ ɐpˈɑːɹt.