At the start of the First World War in 1914 the British Government needed effective communications with front-line troops and replaced messengers on horses with dispatch riders on motorcycles. A number of models were tested for suitability and model H was selected. With the rear wheel driven by a belt, the Model H was fitted with a 499 cc air-cooled four-stroke single-cylinder engine.

More than 30,000 Model H motorcycles were supplied to Allied forces during WWI. Many of the bikes that were used in military service were returned to the factory after the war to be renovated. When the Model H was discontinued in 1923 a total of 57,000 had been produced.