[William Cloud Hicklin]

The closest thing the European Middle Ages had to "specialized shock troops" were the armored knights, especially in the 11th-12th centuries when there was very little that could oppose their charge effectively. These were after all professional warriors (especially during the above era) whose entire job description was (a) fight; (b) train to fight; (c) hunt (as training to fight); (d) participate in tournaments (as training to fight). They started as young as 10 or 11 as apprentices to the military trade, i.e. as squires.

By the High Middle Ages of course the original feudal system (of both economy and caste) had started to break down; both kings and their vassals generally found it more convenient to pay/collect cash taxes which could be used to hire mercenaries, and nobles and the knightly class increasingly found things to do that didn't involve hitting people with cutlery.