Close order formation

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A close order formation is a military tactical formation in which soldiers are close together and regularly arranged for the tactical concentration of force. It was used by heavy infantry in ancient warfare, as the basis for shield wall and phalanx tactics, to multiply their effective weight of arms by their weight of numbers. In the Late Middle Ages, Swiss pikemen and German Landsknechts used close order formations that were similar to ancient phalanxes.

Around the American Civil War (1861–1865), such organizations of soldiers became uncommon since improvements in firearms and artillery had made any such dense formation increasingly hazardous and less effective. The technological concentration of increased firepower to fewer soldiers had rendered the close order formation obsolete by the end of the 19th century. Modern infantry now use skirmish order, which is effectively the opposite of close order.