As did his two older brothers, Manning signed up to participate in WWI, but he was too young - when the War ended, he was still in training, and never saw action overseas.
In the 1920s Manning moved to the United States, living initially with his great uncle, Craven Langstroth Betts, the noted Canadian poet.
[1] In the US, he lived in Manhattan before moving to Staten Island in 1928, where he began writing short stories for several pulp science fiction magazines.
However, In the July, August and September, 1932 issues of Wonder Stories appeared "In the Year 8000", by Otfrid von Hanstein, translated by Manning, teamed with Konrad Schmidt.
For his involvement in the Society, Manning is recognized by the Smithsonian's National Air and Space Museum as an early rocketry pioneer.
Manning married Edith Mary Finette Burrows in 1928 and had three children: Helen Louise, Dorothy, and James Edward.