 One sign of the increasing power of explosives used in land mines was that, by the First World War, they burst into about 1,000 high-velocity fragments; in the Franco-Prussian War (1870), it had only been 20 to 30 fragments.Nevertheless, antipersonnel mines were not a big factor in the war because machine guns, barbed wire and rapid-fire artillery were far more effective defenses.An exception was in Africa (now Tanzania and Namibia) where the warfare was much more mobile.