The percentage of men who were armed with firearms in Tercio-like formations steadily increased as firearms advanced in technology. This advance is believed to be the demise of cavalry when in fact it revived it. From the late 16th century and into the 17th century, smaller pike formations were used, invariably defending attached musketeers, often as a central block with two sub-units of shooters, called "sleeves of shot", on either side of the pikes. Although the cheaper and versatile infantry increasingly adopted firearms, cavalry's proportion in the army remained high.