weapon and all its accessories are carried in an M7 bandolier ("Claymore bag"). The mine is detonated as the enemy personnel approaches the killing zone. Controlled detonation may be accomplished by use of either an electrical or non-electrical firing system. When mines are employed in the controlled role, they are treated as individual weapons and are reported in the unit fire plan. They are not reported as mines; however, the emplacing unit must ensure that the mines are removed, detonated, or turned over to a relieving unit. The M4 electric firing wire on a green plastic spool is provided in each bandolier. The M57 firing device (colloquially referred to as the "clacker") is included with each mine. An M40 circuit test set is packed in each case of six mines. When the mines are daisy-chained together, one firing device can detonate several mines. The mine can be detonated by any mechanism that activates the blasting cap. There are field-expedient methods of detonating the mine by tripwire, or by a timer, but these are rarely used. Development The development of the M18A1 mine dates back to work done during World War II. The Misznay–Schardin effect was independently discovered during World War II by József Misznay, a Hungarian, and Hubert Schardin, a German. When a sheet of explosive detonates in contact with a heavy backing surface (for example, a metal plate), the resulting blast is primarily directed away from the surface in a single direction. Schardin spent some time developing the discovery as a side-attack anti-tank weapon, but development was incomplete at the end of the war. Schardin also spent time researching a "trench mine" that used a directional fragmentation effect. Norman MacLeod and Calord Corporation Following the massed Chinese attacks during the Korean War, Canada and the United States began to develop projects to counter them. Canada fielded a weapon called the "Phoenix" landmine, which used the Misznay–Schardin effect to project a spray of steel cubes towards the enemy. The cubes were embedded in of Composition B explosive. It was too large to be a practical infantry weapon and was relatively ineffective, with a maximum effective range of only 20 to 30 yards (about 20 to 30 meters). Around 1952 Norman MacLeod, at his company the Calord Corporation, began working on a small directional mine for use by infantry. It is not clear if the United States Picatinny Arsenal took the