Replacement of the personnel of an army is called, either by means of voluntary enlistments, by hooks or by fifths.

In ancient times all men, from a certain age, were soldiers. Greece and Rome did not have permanent armies but the youth were ready and ready for war and were preparing to enter the campaign with the same promptness and ease with which the provincials or reserve corps then met. In Athens and Sparta the military age was between 18 and 60 years, although in the last nation the young people were left to save the city and out of the extremely urgent cases, they did not go out to campaign until after 25 years. In Rome, on the days when the enlistments were made, the military tribunes chose from four to four men useful for the service of arms and with them the legions were formed or replaced. The poor of solemnity were exempt from being soldiers, based on the idea that nothing had to defend who had nothing. Of the youngest they formed the light troops or vélites. Then they chose the ostiarios or piqueros: the strongest and most vigorous were destined for princes; the veteran soldiers composed the triarios. The Goths and other nations tumultuously enrolled their troops.

In the Middle Ages, in another place, the army consisted of the contingents of the towns, cities and vassals of the manors. In the sixteenth century, the soldiers were volunteers, not disdaining distinguished characters to belong to this class: the Count of Onate and the Prince of Asculi, among others, were simple pikemen in the third of the famous master D. Sancho de Leiva. When the nobility lost their love of arms and the arts began to provide resources more advantageous and quiet than those of the military for the replacement of the army. In addition to the voluntary hooks that were increasingly scarce, they appealed to the cams, filling the ranks of vagrants and badly entertained and as if this were not enough, civil courts had the power to condemn weapons criminals in a certain class of crimes. Later, knowing the regrettable error in which he had fallen and to moralize the troops, this obligation was established to a certain class of people, which, as is to be presumed, fell on the intimate class of the people. Then came the draws without distinction of classes, the reclosings and substitution were also established.

Diccionario militar, J.D.W.M., 1863

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