Things You Didn't Know About Hitler That Will Blow Your Mind

The feudal system had no state run military. Instead, the military force of the medieval period was fielded by local lords who had sworn fealty to greater lords. These soldiers were a mix of both men at arms and knights. 

A king could command his lords to rally for war, but generally the individual soldier obeyed his lord before the king, as demonstrated by the many rebellions and uprising by local lords against their kings throughout the medieval period. This would have been impossible if the state, or king, controlled the military.

Yet even though this military was fragmented by location and commanders, they still needed a secure place to train and maintain themselves and their arms, rest, and resupply. These places were, of course, the castles and fortified cities of the time (which often had castles within them called citadels), and they served as the medieval soldier’s military base. An army that had access to such a base near a point of conflict held a profound advantage over an attacking force, because they could strike out in skirmishes against a mostly vulnerable aggressor.

Once the skirmish was complete, they could retreat back to a very secure location that couldn’t be attacked in return with such ease. The attacking army could ransack the surrounding land but that didn’t deal with the defending army, which would be striking at their flanks as much as possible. Land was the most valuable resource that an attacking army could take, and land couldn’t be permanently taken until the defending army in that land was dealt with, which meant dealing with the castle.

Of course design was important for defense, and castles were most useful in strategically important locations. But if placed on an advantageously steep, high, or secluded hill, the castle could become nearly impregnable through sheer inaccessibility.

This is especially true in respect to things like siege towers and trebuchets, as they simply couldn’t be used if they couldn’t get close enough. There are many historical castles that were placed in such commanding positions that they were never taken by direct assault.