I'm reading Shogun by James Clevall and the Portuguese characters talk about conquistadors like they're separate from the regular Spanish army, while I thought conquistador was just a label for any Spanish forces conquering New World territory.
A reply to /u/breaksfull
The key differentiation is that the Conquistadors were not organized in the same manner as the King of Spain's armies were at that time. That period saw the founding of the "Spanish Expeditionary Armies", first in Italy under Gonzalo de Cordova, and later the "Army of Flanders" that fought against the revolting Dutch in the Low Countries. Both the army in Italy and the army in Flanders developed a sophisticated system of command, logistics, and training. There was also an increasingly sophisticated system of military justice in place.
To focus on the method of payment, or recruitment, or the training is off the mark, because in reality all these aspects were evolving rapidly in that time period. The Army of Flanders contained many mercenary units. The commanders were often unpaid, rather they expected regional command or nobility titles in reimbursement. Indeed, that early-modern period saw various states struggle with the means by which they were to recruit, maintain, command, and lead armies. Most important was how to fund them.
If we are to agree on the above definition, neither Spain nor Portugal sent an army to the Americas in the early part of the exploration. Although many of the leading Conquistadors were military men, and many Conquistadors became leading military men. Cortés returned to Spain after his conquests in the Americas and was highly decorated by the new king, Charles I Spain / Charles V Holy Roman Emperor. In 1541 he joined Charles V's expedition against Algiers' barbary pirates. Pedro de Candia did the opposite: he first fought in Italy for Charles V, and then went to Peru where he died in battle.
According to Matthew Restall's Seven Myths of the Spanish Conquest, the conquistadors were not soldiers part of the "Spanish" army, if anything they were closer to mercenaries. However, more often than that, they were men interested in being a part of the expedition, or conpania. He has a chart in the book that shows how few were trained militarily as opposed to being normal people like artisans. Furthermore, the expeditions did not have any affiliation with the Spanish military.
(It's my first time contributing and of course the book's at home. I hope I have enough detail.)