On graduation Frank Berryman was granted a commission in the Permanent Military Forces and on 12 November 1915 a commission in the AIF. By now he had the benefit of a significant amount of military training. After six years instruction in the Cadet Corps, six months as a member of the CMF and two and a half years of formal military training at Duntroon, he was setting off for war. Despite his seemingly impressive military record Berryman was only 21 years and 7 months. But youth, determination and contemporary military training were to prove poor preparation for the mass carnage of the Western Front.

As a result of electing to specialise in the artillery Berryman found himself posted as second in charge of the 12th Battery of the recently formed 4th Field Artillery Brigade (4th FAB). Berryman's elation at his commission into the 4th FAB was also shared by fellow Duntroon graduates George Vasey and Edward Milford.

Berryman made an immediate impression on his new comrades. Second Lieutenant Alex Crawford noted that while Lieutenant Vasey was ‘rather hesitant [in] manner and his orders did not have the air of authority’, and Lieutenant Milford was a ‘delightful, gentle natured chap, friendly [and] very likeable’, Berryman was ‘blunt as the back of an axe’ and ‘fanatically keen’, and his commitment to the military was uncompromising. ‘We used to say of Berry that he would cut his grandmother's throat if it was in the interests of the army.’