 Halpern had worked with Moshe Rosenberg since the 1920s in the development of Betar's military programmes and together they conceived of a school for Betar "madrichim".Shortly after becoming director, Halpern recruited the revolutionary Zionist Abba Ahimeir as an instructor of the nationalist youth and together they led the school in an increasingly radical direction in which military training was viewed as a means of establishing the military wing of a national liberation movement.Under the leadership of Halpern (and later of Ahimeir), the 24 cadets took the lead in organising demonstrative activities outside Betar, which notably included taking the initiative in the march to the Western Wall in August 1929.