Crossfire
A crossfire is a military term for the siting of weapons so that their arcs of fire overlap. This tactic came to prominence in World War I.
Siting weapons this way is an example of the application of the defensive principle of mutual support. The advantage of siting weapons that mutually support one another is that it is difficult for an attacker to find a covered approach to any one defensive position. Use of armour, air support, indirect fire support, and stealth are tactics that may be used to assault a defensive position.
Early modern warfare
The concept of overlapping arcs of fire drove major developments in the use of cannon in early modern Europe. The star fort forced attackers approaching the walls into the overlapping enfilade of the protruding bastions; attempts to achieve a similar effect through maneuver on the battlefield were limited by the weight and size of the artillery of the time. The earliest experiments in mobile artillery, such as the leather cannon, were generally flawed due to the limitations of the materials science of the period, but eventually gave rise to the regimental gun.Perhaps the most famous example of crossfire tactics in early modern warfare occurred in the final stages of the First Battle of Breitenfeld. Swedish cavalry under Gustavus Adolphus outflanked and seized the artillery pieces of the Imperial army. As the battle had progressed, the Imperial guns were now well-positioned to fire upon the bulk of the Imperial army, and the crossfire of Swedish and captured cannon shattered the Imperial forces.