In 1871 during the Franco-Prussian War, when Paris was surrounded by Prussian troops, the French military used hot air balloons to transport homing pigeons past enemy lines. Microfilm images containing hundreds of messages allowed letters to be carried into Paris by pigeon from as far away as London. More than one million different messages travelled this way during the four-month siege. They were then discovered to be very useful so were used in World War One.
The UK maintained the Air Ministry Pigeon Section during World War II and for a while thereafter. A Pigeon Policy Committee made decisions about the uses of pigeons in military contexts. The head of the section, Lea Rayner, reported in 1945 that pigeons could be trained to deliver small explosives or bioweapons to precise targets. The ideas were not taken up by the committee, and in 1948 the UK military stated that pigeons were of no further use. However, the UK security service MI5 was still concerned about the use of pigeons by enemy forces. Until 1950, they arranged for 100 birds to be maintained by a civilian pigeon fancier in order to prepare countermeasures.[clarification needed] The Swiss army disbanded its Pigeon section in 1996.