to firearms tended to work as long as the velocity and weight of the ball remained quite low, but over time the increasing power and effectiveness of firearms overtook the development of defenses to counteract them, such that flintlock muskets (entering use after 1650) could kill an armoured man at a distance of even 100 yards (though with limited accuracy), and the armour necessary to protect against this threat would have been too heavy and unwieldy to be practical. The flintlock musket, carried by most infantrymen other than pikemen after 1650, fired a heavier charge and ball than the matchlock arquebus. A recruit could be trained to use a musket in a matter of weeks. Operating a musket did not require the great physical strength of a pikeman or a longbowman or the fairly rare skills of a horseman. Unlike their arquebus predecessors, flintlock muskets could neutralize even the most heavily armoured cavalry forces. Since a firearm requires little training to operate, a peasant with a gun could now undermine the order and respect maintained by mounted cavalry in Europe and their Eastern equivalents. Although well-smithed plate-armour could still prevent the penetration of gunpowder-weapons, by 1690 it had become no match for massed firearms in a frontal attack and its use ended, even among the cavalry. By the end of the 17th century, soldiers in the infantry and most cavalry units alike preferred the higher mobility of being completely unarmoured to the slight protection, but greatly lessened mobility, offered by donning the heavy plate armour of the period. Transition to flintlock muskets The arquebus, in use from 1410, was one of the first handheld firearms that were relatively light (it still required a stand to balance on) and a single person could operate one. One of these weapons was first recorded as being used in the Battle of Agincourt in 1415, although this was still very much a medieval battle. The term musket originally applied to a heavier form of the arquebus, which fired a shot that could pierce plate armour, though only at close range. In the 16th century it still had to be mounted on a support stick to keep it steady. The caliver was the lighter form of the arquebus. By 1600, armies phased out these firearms in favour of a new lighter matchlock musket. Throughout the 16th century and up until 1690, muskets used the matchlock