Interested in any period before the introduction of gunpowder weapons. Frequently when I read about sieges there is mention of trenches being occupied by defenders, as well as by the besieging force to defend against relief. My question is what role did occupied trenches play in warfare, if any?
In pre-modern battles, especially field engagements, trenches were not dug in order for troops to stand around inside them in a sort of WWI fashion. Medieval weaponry, such as lances, swords, and bows, couldn't be wielded as easily inside of the narrow confines of a trench. Generally, their purpose was to serve as a barrier/obstacle between the enemy and one's own forces. While a shallow, hastily dug ditch would not permanently stop an enemy from moving over it, it would certainly disrupt their advance and prevent them from maintaining proper order as they attacked. Trenches and ditches also served as a shield from cavalry charges. Missile troops used ditches and other field fortifications like wooden palisades and hedges in order to defend their positions. The fortifications helped distance the soldiers from the enemy as well as funneling attacking troops into killing zones, where their formation was compacted and it would be easier to hit their targets.