Definition of the word level against

The expression "level against" has its roots in the peculiar circumstances of medieval siege warfare. During these times, an army laying siege to a fortified town or castle would typically construct makeshift defensive walls, known as "siege engines," around its perimeter. These walls, made of earth and wood, would provide cover and protection to the besieging soldiers as they bombarded the enemy stronghold from a distance. The primary target of these siege engines was the defensive walls and towers of the besieged town or castle, which had to be breached in order to gain entry. In order to achieve this, the attacking army would build their siege walls as close as possible to the enemy's defensive walls, essentially "leveling" them against each other. The word "level" in this context refers to making two surfaces identical in height, in order to facilitate an attack. When the besieging army's walls were "leveled against" the enemy's walls, this created a narrow gap, known as a "breach," through which the attackers could send in storm-troopers and make their way into the castle or town proper. This term is still used in modern warfare, as well as in other contexts where it is necessary to achieve parity or equality between two separate entities in order to accomplish a goal. In essence, "level against" is a military term that has passed into common usage in order to better describe circumstances where mutual alignment is necessary in order to overcome an obstacle.