What is "sapping"

Sap \Sap\, v. t. [imp. & p. p. Sapped; p. pr. & vb. n. Sapping.] [F. saper (cf. Sp. zapar, It. zapare), fr. sape a sort of scythe, LL. sappa a sort of mattock.]

1. To subvert by digging or wearing away; to mine; to undermine; to destroy the foundation of.

   Nor safe their dwellings were, for sapped by floods, Their houses fell upon their household gods.
   --Dryden.

2. (Mil.) To pierce with saps.

3. To make unstable or infirm; to unsettle; to weaken.

   Ring out the grief that saps the mind.
   --Tennyson.

n. The act by which something is sapped or depleted. vb. (present participle of sap English)

1. n. a watery solution of sugars, salts, and minerals that circulates through the vascular system of a plant

2. a person who lacks good judgment [syn: fool, saphead, muggins, tomfool]

3. a piece of metal covered by leather with a flexible handle; used for hitting people [syn: blackjack, cosh]

4. [also: sapping, sapped]

1. v. deplete; "exhaust one's savings"; "We quickly played out our strength" [syn: run down, exhaust, play out, tire]

2. excavate the earth beneath

3. [also: sapping, sapped]

See sap

Sapping is a term used in siege operations. Any trench excavated under defensive musket or artillery fire that was intended to advance a besieging army's position in relation to the works of an attacked fortification was referred to as a sap. Saps of approach were excavated by brigades of trained soldiers, often called sappers, because they dug the saps, or specifically instructed troops of the line.

By using the sap (trench) the besiegers could move closer to the walls of a fortress, without exposing the sappers to direct fire from the defending force. To protect the sappers, trenches were usually dug at an angle in zig-zagged pattern (to protect against enfilading fire from the defenders) and at the head of the sap a defensive shield made of gabions (or a mantlet) could be deployed.

Once the saps were close enough, siege engines or cannons could be deployed to batter a breach in the curtain walls. Prior to the invention of large pieces of siege artillery, miners could start to tunnel from the head of a sap to undermine the walls. A fire or gunpowder would then be used to create a crater into which a section of the fortifications would fall creating a breach.