With the development of the chained, self-propelled two-wheeled transport known as The Bicycle in the late 19th and early 20th Century, personal transportation advanced a massive step. Very quickly, this firm of transportation saw applications in all facets of business and industrial use as well. No longer was "Horse Power" the dominate form of "movement". Mail, Courier and delivery of goods could all be managed faster and more effectively. Therefore, when Man went to "War", so did this new invention.
The development of pneumatic tires (vulcanized rubber), further increased the effectiveness of The Bicycle. As early as 1887, France was among the first Nations to develop The Bicycle for use in it's Military. Seen as a way to quickly move Infantry, unlike a Horse, The Bicycle did not need to be "caught or fed". A Soldier carrying 80-pounds of equipment could effectively move (even in Formation) with ease.
Couriers and Messengers on the battlefield could deliver Orders and critical information from Field Commanders to Headquarters much more easily than by Horse (although "Old Cavalrymen" would argue this!). By World War I, Great Britain and Germany had fielded Bicycle Infantry with great success. This was made even more so by the vast amount of paved roads that covered most of Europe (to make use of the equally "new" use of The Automobile and the advent of newer "Wheels if War" - which would spell an end to even The Bicycle as a War transport).
In America, attempts to capitalize on The Bicycle for Military use was made. The famed 25th Infantry (The "Buffalo Soldiers"), were outfitted with Bicycles. Training established held that they could achieve 800 to 1,900-miles in sustained maneuvers. However effective, as stated - The rapid development of The Automobile would spell an end to the official use of Bicycles Militarily. Some would still be pressed into Service during World War II.