This topic often fascinated me as a kid. I often questioned myself if there was an equivalent of the use of machinery to protect ground soldiers during a siege or an attack at some city or whatever war was involved.
Reading the Wikipedia article for Mechanized infantry, it mentions that Mech inf (for short) are infantry equipped with armored personnel carriers or infantry fighting vehicles and it shows a picture of a M113.
But continuing reading I found that there were other vehicles used for such purposes, such as tanks and hybrid vehicles with ordinary vehicle wheels and caterpillar tracks.
I often thought that the term would be applied only to vehicles similar to the M113 but it looks like this isn't the case. Thus my question arises - if in history of warfare, this concept can be extended to other similar mechanical apparatus used by different civilizations.
Searching my memory, I recall the phalanx formation, or the mythical Trojan Horse. Is this an attempt at mechanized infantry? How about battering rams used in the middle ages? I know in East Asia, Koreans had the Turtle ship and this doesn't count if we consider that what I'm asking moves on land and not by sea. I also forgot to mention Da Vinci's supposed tank (not sure if he did build one) and I also remember James Burke's Connections program mentioning something about Gustavus Adolphus at the Battle of Leipzig during the Thirty Years War: he used men armed with pikes and muskets. But again, I don't think this constitutes a mechanized infantry, maybe just a combined arms operation?
Anyways, when does this concept really began? Is there any evidence of similar things used in the ancient world, middle ages and beyond?. Moreover, during the recent Libyan war in 2011 I noticed rebels used ordinary vehicles attached to guns which the media called "technical" (for those improvised vehicles). Can these be called Mechanized infantry?. What do books say about the definition of Mech infantry used by most NATO countries today?
I hope someone can help me to get a clearer idea of all this.