Brillant started his mechanical engineering studies in the Hebrew Technion, and in 1937 he joined the Hagana Flight Club in "Kfar Yeladim" at Jezreel Valley as an instructor. The Kfar Yeladim flight club was the early seed of the Hagana for creating an air-arm, later became the Israeli Air Force, under the guise of a gliding club. In 1938, he volunteered in the Palestine Police Railway Department (PPRD) of the Hagana Ghaffirs of the Jewish Supernumerary Police, and escorted trains from Zemach at the Sea of Galilee to Port Said, Egypt. During service in the PPRD, he was wounded when his train was damaged by a mine placed by terrorists during the Arab rebellion of 1936-1939. He discharged himself from hospital and returned to his company.