Sortie

An attack conducted by the garrison of a fortification under blockade, investment, or attack by regular approaches for the purpose of disrupting the enemy's operations against the fortified place was referred to as a sortie. Sorties were useful for enforcing caution on a besieging force and requiring it to use greater resources and extra time in establishing and advancing their trenches of attack. One or two strong sorties by a garrison could compel the attacking force to keep a greater number of troops in the trenches for longer periods of time to act as trench guards and cover the operations of working parties laboring to construct batteries and other works. A successful sortie which drove besieging troops from their advanced trenches could also delay the advance of the attack by filling in trenches and burning materials collected in and under cover of the trenches.

In general, a sortie was launched from the salient or re-entering places of arms of covered way or from behind other outworks, such as tenailles, that covered the force from the enemy's view. Issuing from the defensive works suddenly at an unexpected hour the garrison detailed for the sortie would charge forward rapidly across the glacis and attempt to surprise the besieging force's trench guards before they could line their trenches to oppose the assault. If this was accomplished a second working party would follow behind the assaulting troops and immediately begin destroying the besieging army's trenches. This demolition continued until the besieging army's trench guards were reinforced and advanced to recover their lost works or the work was completed and the troops conducting the sortie retired back to their defensive works.

Sorties were generally considered quite risky for the garrison since the assault could result in an unfortunate number of casualties that would effectively reduce the garrison's strength and ability to endure the fatigue of a prolonged resistance. There was also the possibility that the besieging army's trench guards could be rapidly reinforced, counterattack, rout the assaulting troops, pursue them, and break into the defensive works as the routed troops attempted to re-enter the fortification. These liabilities tended to enforce a certain degree of caution on the conduct of sorties; for the most part sorties were conducted using a limited number of troops with very limited objectives: the main objective always being the safe return of the assaulting troops. This is the thing that distinguished a sortie from other types of attacks (such as an attempt to break the siege) that could be carried out by a besieged garrison: the assumption, from beginning to end, was that the assaulting force would return to the fortification and continue to defend it.

January, 2003