Kammala jumla mai zuwa: An haifi Armstrong a ranar 11 ga Yuni 1897 kuma ya yi karatu a Kwalejin Cheltenham. Bayan ya halarci Kwalejin Soja ta Royal Sandhurst, an ba shi izini a cikin East Surrey Regiment a watan Afrilu 1915. An tura shi zuwa Machine Gun Corps, ya yi aiki a Faransa daga 1916 zuwa 1918, inda aka raunata shi sau biyu kuma, a watan Maris na 1918, ya zama fursunonin yaki. An dawo da shi a watan Disamba na 1918, ya yi aiki a Arewacin Rasha a 1919 kuma an ba shi lambar yabo ta Soja don ƙarfin hali. Ya kasance a cikin
Mesopotamia 1920-21 da kuma kan iyakar Arewa maso Yammacin Indiya 1930-31, yana ba da yawancin aikinsa na tsakanin yaƙe-yaƙe tare da Bataliya ta 1, East Surrey Regiment a Masar, Sudan, Hong Kong da Indiya.