After World War II , he served as Executive Secretary of the Preparatory Commission of the United Nations in August 1945 , being appointed Acting United Nations Secretary-General from October 1945 to February 1946 until the appointment of the first Secretary-General Trygve Lie .
He was appointed Acting United Nations Secretary-General from October 1945 to February 1946 until the appointment of the first Secretary-General Trygve Lie .