James Harold Manning was born at Saint John, N.B., on February 15, 1897, the second son of Dr. James and Helen Hanington Manning. Hew was educated at the Saint John Public Schools, and graduated from the High School in 1912. On graduating he took the City Corporation Gold Medal for general proficiency, and the Ellis Gold Medal for the English Essay.

During 1913 and 1914 he was employed with the Engineers of the Public Works Department of Canada in the harbor of Saint John. In 1914 he decided to take up the study of Dentistry, and went to Philadelphia, where he entered the University of Pennsylvania. It was during that year that the Great War broke out in Europe. On the completion of a successful Freshman year in 1915, and being eighteen years of age, he returned to Saint John and obtained a commission as Lieutenant in the 104th Battalion, CEF, then being raised by Lieutenant-Colonel George W. Fowler. Subsequently he was transferred to the 140th Battalion, training with them at Valcartier Camp in 1916, and going to England on a Special Supernumerary Draft of Officers. This draft was at once sent to Crowborough Military School, where he was placed in the advanced Field Officer's Course, making in the final examinations the fine average of 92.60 on all subjects (a most unusual performance). Having been posted in G.O. as Lieutenant with the 52nd Battalion, CEF (Port Arthur), he crossed to France in February, 1917. This fine corps saw much severe fighting during the war and had especially heavy losses. It was decimated at Paschendaele but attained its objective.

It was during the battle of Vimy Ridge that he was wounded in the arm by a shell, and was invalided home to England for three months. On recovery he rejoined his corps, the 52nd, at Lens during the fierce fighting that raged without intermission amongst the coal mines and slag heaps of that disputed territory.

On August 27th, 1917, while he was carrying out a minor operation between the lines for the capture of three German machine guns, an error in elevation was made by the British Artillery, nine miles in the rear. Unfortunately their barrage was laid down where he and his detachment were waiting, which was promptly added to by the enemy. Wires were cut by gun fire and word could not be sent to the guns to increase their range. Manning was completely buried by the explosion of a big shell but was dug out again by his sergeant. Collecting with difficulty some seven or eight men he rushed the machine guns, from which the Germans fled, and brought them into the Canadian lines – winning success out of disaster. It was at the very close of this affair that a whiz-bang burst close behind him, throwing him violently to the ground, and shattering his left hand. This terminated his military service. Lieutenant-Colonel Forster, of the 52nd (now Major General Forster, V.C.), writing of him at that time, said "He is a born leader of men…"

After a long period in hospital in England he was invalided home to Canada, where an attempt was made to save his hand by grafting in new tissue, but without success, and he was finally discharged from active service with a life pension in 1918.

Owing to the loss of the use of his left hand he was obliged to abandon his degree in Dentistry, and entered Acadia University at Wolfville, Nova Scotia, for an Arts Course. He registered as a junior, and in one year he completed sufficient units of work to qualify for graduation. After due consideration he decided to take up the study of Town-planning and Landscape-gardening, and in 1919 entered Harvard University. He was appointed to the Town-planning staff of Boston. From there, he went to Chicago, participating in Town-planning there as well. From there, he left for New York in 1922 where he worked on the draughting staff of the Electric Bond and Share Company. That same year, he accepted a position on the Engineering Staff of the Standard Oil Company of New Jersey, for service in Maturin, Venezuela. He worked there until the Spring of 1924, when he died of hemmorhagic fever brought on by malaria. His immediate superior on the staff of the Standard Oil Co. – Mr. Acton Gerlach – wrote: "For the past six months he had been located in the Maturin district as a member of our engineering staff, and we had all come to know him and to be fond of him; to admire the fine traits of his character and to respect the admirable qualities of his mind. It was a pleasure to all of us to be associated with one who so well embodied those ideals of thought and conduct that are the heritage of gentlemen…"

Despite his success and friendships overseas, he often thought of home, writing:

If I were ruler of this land, with majesty complete,
If I owned all these many leagues, and not a yard beside,
I'd give them up without a sigh for room to place my feet
By the fog-banks and the rain, and the sound of Fundy's tide.

Manning's life had been one of condensed concentrated effort – as if he somehow felt that his span of life was to be all too short and that he must hasten. His studies commonly carried him far into the night, yet did he find time to do a vast amount of reading and writing. During his twenty-seven years he went farther afield than most men of sixty. At the time of his landing in France to join the 52nd he spoke and wrote both French and German fluently. To these were added Latin, Greek, Italian, Spanish and Russian. But although a brilliant linguist his special aptitude was in the field of English literature. His prose was dignified and graceful, the words being most aptly chosen; but poetry was his own special delight. His note books, letters, envelopes and memorandum books were all full of casual verse and stanzas that haunted him until he had jotted them down. Finally he gave himself in earnest to the writing of poetry, and in what spare time he had, managed to produce quite a considerable amount of verse.