The radio programme details how many of the animals were rounded up from their quiet lives on Irish farms and sent to war where they were shelled and drowned in mud.
Many perished from disease, while others died being transported in cramped, overcrowded ships to Europe.
They Had No Choice — The Irish Horse at War also tells of how soldiers formed extraordinary bonds with their horses, even risking their lives to save their animals.
War horse expert Ronan Wilson, from the Wolftrek Equestrian Centre in Blessington in Co Wicklow, said the majority of heavy-legged, Irish horses didn’t stand a chance of escaping gunfire on the battlefield while weighed down with ammunition and supplies.
“They weren’t the glamorous, shiny-coated horses you would see outside Buckingham Palace. They were hairy-legged, heavy cobs that probably had been pulling barrels out of Guinness in Dublin.
“These poor guys were weighed down with 17 stone or 20 stone trying to get through that type of terrain. Not being fast or manoeuvrable, when an artillery barrage came in they could have done nothing. They had nowhere to hide, nowhere to cover. A horse can’t jump into a trench.”
The documentary reveals that 80% or more of the horses killed in the war were draught horses used to carry ammunition.
Horses were bought up by the British army through a network of army agents, dealers, and vets and at fairs. Herds were driven through the streets to the ports, and the programme reveals several jumped over the railings in panic and drowned.