An entrenching tool, E-tool, or trenching tool is a collapsible spade used by military forces for a variety of military purposes. Survivalists, campers, hikers and other outdoors groups have found it to be indispensable in field use. Modern entrenching tools are usually collapsible and made using steel, aluminum, or other light metals.
Entrenching tools go back at least to the times of the Roman Legion. Julius Caesar, as well as other ancient writers, documented the use of spades and other digging implements as important tools of war. The Roman Legion when on the march would dig a ditch and rampart around their camps every night where established camps were not available.
Siege tactics throughout history required the digging of fortifications and often mining of walls was attempted, where saps were dug to a wall’s foundation, and collapsing the wall was attempted.
In more modern times the siege tactics of the Napoleonic Wars used spades and pickaxes as entrenching tools to dig trenches towards the walls of the fortifications being besieged, to allow men and munitions to get close enough to fire cannons at the walls to open a breach. Being too long and heavy to be transported by individual soldiers, entrenching shovels and spades were normally carried in the supply carts (logistics train) of a military column; only pioneer or engineer troops typically carried spades or shovels as part of their individual equipment. This frequently led to situations in which the infantry did not have access to entrenching equipment when it was needed. As one U.S. army infantry officer noted, "the intrenching [sic] tools of an army rarely get up to the front until the exigency for their use has passed."
In 1870, the U.S. Army introduced the trowel or spade bayonet, intended for individual soldiers as both a weapon and an entrenching tool. This was followed by the development of separate trowel and spade tools, small one-hand implements that could be carried as part of a soldier's individual equipment. While the entrenching trowel or spade gradually gave way in the U.S. and other modern armies to larger, heavier, and more effective entrenching tools, the concept of supplying each infantry soldier with a means of digging his own entrenchments or breastworks continued as a tactical doctrine.