The men had initially been rejected for war service as they failed to meet the minimum regulation height.
But they tenaciously lobbied MPs and other people of influence and were eventually allowed to join up.
At first, they were restricted to their own bantam battalions but after 1916, those who were still deemed fit for military service were absorbed into 'normal' army units.
The story of these bantam soldiers, known as the The Wee Fellas and whose number included Billy Butlin, who was part of a Canadian battalion, has now been reflected in a novel by Ken Houston, an Edinburgh-based PR company owner.
Mr Houston, writing as Richard Maitland, visited such battlefields as Arras and the Somme in order to research the book, The Wee Fellas.
"The bantam battalions did not begin to be formed until early 1915," he said.
"By then, a lot of the early general enthusiasm for the war was starting to evaporate and people knew it was going to be a long slog.
"The men who were under 5ft 3ins in height did not have to volunteer.
"If conscription had been introduced, they would not have been conscripted, on the basis of their lack of height.
"Individually, you have to admire what they did during the war.
"They could quite easily have sat out the war but they chose to volunteer their services."
The book focuses on a Glasgow billiard-hall manager and protection racketeer who volunteers as a bantam out of self-preservation rather than patriotism.
It was inspired by the real-life bantam battalion, the 18th Highland Light Infantry, which attracted more than 2000 volunteers within days of being raised in Glasgow in February 1915.
"A battalion is 1000 in strength and in Glasgow there were enough volunteers for a second bantam battalion, the 14th HLI," he said.
Other battalions were raised in Edinburgh (the 17th Royal Scots) and in Hamilton, Lanarkshire (the 13th Cameronians).
Similar battalions were established across England and Wales, from the northern industrial cities, where many volunteers had worked as miners, but also from rural areas.
All told, some 50,000 bantam soldiers joined up, across the UK and Canada. Mr Butlin, who would later become the holiday-camp entrepreneur, joined the 216th (Bantams) Battalion, part of the Canadian Expeditionary Force.
"A lot of the volunteers in this country were aggressive by nature, and a lot of them proved to be good soldiers," Mr Houston added.
"In the case of those who were either discharged, or assigned to duties behind the front line, the issue was probably as much to do with their lack of weight as their lack of height.
"War historians have tended to mention the bantam soldiers only in passing, and then in relation to the brawls many of them got involved in, but I was keen to explore the wider picture in my book."
The Wee Fellas is available on Kindle and in paperback from Amazon and bookshops.