American Motorcycles of World War I
When the United States entered World War I in April 1917, the Army needed fast, flexible transportation that could carry messages, riders, small loads, and sidecar equipment without waiting for a horse team or a truck column. Motorcycles filled that gap. They were not tanks, and they were not a replacement for artillery or infantry, but they gave the Army a quicker way to move men and orders across camps, military roads, rear areas, and, in limited cases, roads close to the fighting in France.
The bulk of the American motorcycles came from Indian and Harley-Davidson. Indian committed almost all of its wartime production to the military and built nearly 50,000 machines for the war effort. Harley-Davidson also increased production and delivered about 20,000 military motorcycles. Excelsior, Henderson, Cleveland, and a few other American manufacturers supplied smaller numbers, but Indian and Harley-Davidson remained the two names most closely tied to U.S. military motorcycles of the First World War.
Why the U.S. Army Needed Motorcycles
The Army had already seen what motorcycles could do before the United States officially entered the war. Early military experiments and border service helped prove that motorcycles could move faster than mounted messengers and could cover ground that was slow or wasteful for larger vehicles. The 1916 Punitive Expedition against Pancho Villa had already put motorcycles into an active field campaign. By 1917 the Army was not starting from zero. Earlier military motorcycle trials had already shown the basic idea, while later field testing along the Mexican border at Fort Brown gave the Army a better look at what motorcycles could do outside parade-ground conditions.
By 1917, the motorcycle was useful because it was quick, narrow, and mechanically simple compared with a truck. Dispatch riders could carry written orders between headquarters and units. Motorcycle scouts could ride ahead of a convoy or patrol a road. Military police could use them for traffic control. Training camps used them to prepare drivers and mechanics. In that sense, the WWI motorcycle sat between the horse-mounted messenger and the fully motorized Army that would follow in later decades. That experience also helps explain why motorcycles appealed to an Army still rooted in horse cavalry but beginning to test faster machines for scouting, messenger work, and liaison duty.
Indian PowerPlus: The Army’s Big Supplier
The Indian military model was based on the company’s PowerPlus Big Twin. It used a 61 cubic inch side-valve motor that produced about 18 horsepower and could reliably carry the motorcycle at speeds around 60 mph. The engine was mated to a three-speed hand-shift transmission, and the drive train was mounted in a frame with both front and rear suspension. Lighting was handled by a gas headlamp, and there was a rear brake for stopping.
Indian’s heavy wartime commitment meant that many civilian dealers had little left to sell while the Army was buying motorcycles. That decision gave the military a large supply of PowerPlus-based machines, but it also tied Indian very closely to the war economy. For the Army, the appeal was straightforward: the PowerPlus had enough torque for sidecar work, enough speed for dispatch duty, and enough mechanical strength to serve as a practical military workhorse.
Harley-Davidson J Series: Milwaukee Goes to War
Harley-Davidson based its military motorcycle on the J-series machine. It used a 61 cubic inch F-head V-twin that produced about 15 to 16 horsepower, putting it slightly below the Indian in terms of rated power. Like the Indian, the Harley used a three-speed hand-shift transmission. It carried front suspension, a rear brake, and a simpler gas headlamp in place of the electric lighting used on civilian models.
Harley-Davidson did not supply as many motorcycles as Indian, but the company still delivered roughly 20,000 military machines. The wartime J-series Harley became a familiar sight in training, dispatch, and sidecar service, and its basic layout made it adaptable to the same mix of escort, communications, and utility jobs that military planners expected from motorcycles in 1917 and 1918.
Sidecars made the motorcycle far more useful to the Army. A solo machine was quick, but a sidecar outfit could carry a passenger, a gun mount, a stretcher, tools, extra equipment, or a second soldier. That versatility is why so many WWI military motorcycle photographs show three-wheel outfits rather than solo dispatch bikes alone.
Excelsior, Henderson, Cleveland, and the Smaller Makes
Indian and Harley-Davidson supplied the bulk of the motorcycles, but they were not alone. Excelsior and Henderson also delivered machines in much smaller numbers, and Cleveland and other smaller American makers appear in limited training, dispatch, or support roles. The exact totals for these smaller manufacturers are less certain than the Indian and Harley figures, so they are best treated as limited contributors rather than equal suppliers.
| Make / model | Engine and power | Military notes |
|---|---|---|
| Indian PowerPlus | 61 cubic inch side-valve V-twin, about 18 hp | Large-scale U.S. military supplier; three-speed hand shift, gas headlamp, rear brake, front and rear suspension. |
| Harley-Davidson J series | 61 cubic inch F-head V-twin, about 15–16 hp | Major U.S. military supplier; three-speed hand shift, front suspension, gas headlamp, rear brake. |
| Excelsior | Approximate 61 cubic inch IOE V-twin; period figures vary | Smaller wartime supplier; less common in U.S. service than Indian or Harley-Davidson. |
| Henderson | Four-cylinder models in limited numbers; period figures vary | Specialty and smaller-quantity use; exact procurement totals are less clear. |
| Cleveland and other smaller makes | Lightweight singles and other smaller machines | Limited dispatch, training, and support roles where smaller motorcycles made sense. |
What WWI Motorcycles Actually Did
The most important job was communication. A dispatch rider could carry physical orders, maps, messages, and small items between headquarters, supply sections, and field units. Motorcycles also led convoys, checked road conditions, and helped keep traffic moving around camps, ports, depots, and roads crowded with men and equipment. Outside Army units, the American Red Cross Flying Squadron used a Harley-Davidson sidecar outfit as part of its emergency fleet in London.
That does not mean every American motorcycle went directly into combat in Europe. Many remained stateside for training, drill, convoy practice, military police work, and Signal Corps or transport duties. Some served in France and Belgium during the late-war period, but the motorcycle’s real value was support and speed rather than heavy combat. Stateside motorcycle duty also stretched into specialized patrol work, including coastal watch and beach service where speed and a small footprint mattered more than heavy equipment.
Motor Mobile Infantry and Sidecar Weapons
Period accounts used the term “Motor Mobile Infantry” for motorcycle-equipped troops trained to move quickly and support larger units. In photographs, that idea often appears in the form of sidecar-mounted machine guns. These outfits looked dramatic, and they gave soldiers a mobile platform that could be moved faster than a heavy gun on foot. The same sidecar-gun idea also appeared in home-front training, including a 1918 Police Reserve women’s machine-gun squad with a Lewis gun mounted on an Excelsior outfit.
In practice, the trench warfare of 1918 limited how often motorcycles could be used like true mobile combat vehicles. Roads were damaged, mud was everywhere, and the front was crowded with artillery, supply traffic, horses, trucks, and infantry. Sidecar machine-gun outfits were useful as mobile fire platforms and training or security tools, but the motorcycle’s strongest wartime role remained communication, patrol, and light transport.
Motorcycle Ambulances
Ambulance sidecars were another important military adaptation. A motorcycle could be fitted with a stretcher carrier to move one wounded man, and some arrangements could carry more than one casualty depending on the sidecar frame and equipment. These machines were not a replacement for full ambulances, but they could be quicker and more maneuverable in places where larger vehicles were slow, unavailable, or blocked.
The same sidecar logic applied to gun mounts and other military equipment. The motorcycle supplied the speed and the engine; the sidecar supplied the working platform. That combination made Indian and Harley-Davidson twins far more versatile than a solo machine.
The photo record also shows smaller makers in the wartime mix. Excelsior did not match Indian or Harley-Davidson in military volume, but its machines were part of the broader American motorcycle industry that the War Department drew from during the conflict.
How Many Reached the War Zone?
The production numbers can make it sound as though tens of thousands of American motorcycles were all fighting in France, but the reality was more complicated. Indian built nearly 50,000 military motorcycles, and Harley-Davidson built about 20,000, yet many machines stayed in the United States for training, camp work, convoy exercises, dispatch service, and maintenance schools.
Only a fraction of the total American motorcycle output reached the Western Front before the Armistice. Late-war deployments included hundreds of Harley-Davidson J-series machines in France, where motorcycles were assigned into transport, divisional, and dispatch work rather than independent motorcycle regiments. After the Armistice, motorcycles continued to be useful for occupation, supply, and liaison duties while the Army unwound the massive wartime transportation system it had built in a hurry.
The surviving photographs are valuable because they show the motorcycle in all of these roles: solo transport, dispatch riding, sidecar work, ambulance conversion, machine-gun demonstration, and general military utility. Together, they show why the motorcycle mattered even when it was never the biggest machine in the war.
The Corporal Holtz Photograph
The final photograph in this set has one of the more interesting caption problems in the archive. It was widely repeated with a dramatic story attached to it, but the real Holtz story is more complicated than the newspaper version. I cover the full Holtz story separately, since that image deserves more than a one-line caption.
The American military motorcycle story did not begin with the familiar World War II WLA. WWI machines from Indian, Harley-Davidson, Excelsior, Henderson, Cleveland, and other makers helped prove where motorcycles were useful: dispatch riding, convoy work, patrol, traffic control, sidecar ambulance service, and specialized sidecar equipment. They were not the dominant weapon of the war, but they were part of the Army’s move away from horse-only mobility and toward a more motorized military.