Leak was evacuated to the United Kingdom, and did not return to his unit until October 1917. Suffering from the effects of his service, Leak was convicted of desertion by a court-martial in November, but his sentence was ultimately suspended, and he returned to the 9th Battalion. In early March 1918 he was gassed, and did not rejoin to his unit until the Armistice of 11 November 1918. He returned to Australia and was discharged in 1919.