In the South African War a disaster to a Convoy at _Sannah's Post_, or _Koorn Spruit_ (March 31, 1900), was caused by the absence of precautions in front of a retreating force, the wagons being permitted to enter a defile (the Spruit crossed the road at right-angles and was held by the Boers) before the exit had been secured. Earlier in the same campaign a Convoy of 800 wagons was lost at _Ramdam_ (February 13, 1900). An ambushed force of Boers killed all the transport animals and the wagons were abandoned. No escort had been provided for the Convoy, which entered the ambushed area without previous reconnaissance. Throughout the South African War the activities of De Wet emphasised the vulnerability of the Lines of Communications.
Where the tactical situation permits, arrangements should be made to protect the Lines of Communications by offensive action. An engagement may be invited in a suitable position, the protecting troops holding the raiders with a Delaying Action while reinforcements are summoned to converge on the battlefield for the purpose of surrounding and exterminating the raiders.
A Rear Guard is essential to a force advancing in order to pick up the stragglers, to keep off marauders, and to prevent surprise by an energetic enemy who may detach a force for a surprise attack on the rear of the advancing column.
But its most important work is the protection of a retreating force, and this work will vary in difficulty with the freshness and enterprise of the enemy and the spirit and determination of the force that is being pursued. Generally speaking, Rear Guard fighting against an unexhausted enemy is the most difficult and most dangerous of all military enterprises. When a Rear Guard halts to fight it is being separated every minute from the Main Body, which is moving away from it, while every minute brings reinforcements to the enemy. The work requires great tactical skill, as it is the duty of the commander to delay pursuit by occupying positions from which he withdraws at the last moment, without becoming involved in a general engagement, from the meshes of which it may be necessary for the Main Body to return and extricate him. The work also requires great moral courage, as it is the duty of the commander to risk the loss of his force if by so doing he is adopting the only means of saving the Main Body.