Explosive devices engineered to detonate by pressure on contact or by proximity are used as antitank, antipersonnel and antivessel weapons. They may be employed by regular military forces, by guerrillas, by terrorists, by saboteurs or by criminals. In large numbers, such land or naval mines afford the opportunity that one or more will escape detection and minesweeping removal actions. Such derelict naval mines, fixed or floating free, remain a threat to ships at sea or coming into ports. Unremoved land mines are a hazard to any vehicles, persons, livestock or single animals in the vicinity.
Land mines made their first appearance (together with poison gas) in World War I, when Germans buried fused artillery shells to counter allied tank offensives. In the 1920s, the use of chemical weapons was successfully outlawed, in part because belligerents had a mutual interest in respecting the ban. By contrast, landmines were less obviously horrifying, easier to use than chemical weapons, and had the tactical benefit of forcing tanks into narrow passages that had been swept of mines. Soon, light, easy-to-handle explosives made possible anti-personnel bombs that could be detonated by a footfall.
By the middle of the 1990's it was estimated that there were 80 to 110 million unswept landmines in 64 countries worldwide. Afghanistan, Angola and Cambodia were thought to contain 28 million mines, and 22,000 mine-related casualties had occurred in these countries each year. Africa had more than 20 million landmines, killing 12,000 people a year, mostly civilians. Iraq, Sudan, Mozambique, Somalia, Ethiopia and Eritrea contained more than 1 million mines each. In 1993, 80,000 landmines were extracted worldwide at a cost of $200 to $1000 per extraction, and 2.5 million mines were implanted at a cost of $3 each.
Mining of the Suez Canal in 1984 by unknown saboteurs was not effectively countered by sweeping, and ships were damaged. Newer mining armaments technology may include non-metallic, undetectable mines; 'smart' naval mines that move; and systems approaches to land mining, particularly around fixed tactical or strategic installations, that are not possible to sweep (such as time-delay fuses on nylon-canistered devices, or C-B mines). The material remnants of war, particularly mines and unexploded bombs have been left on the territories, most recently in developing countries. These materials seriously impede development and cause injuries and the loss of lives and property. In situations such as in Angola in 1993 where fighting continues intermittently reliefs supplies are cut off. People faced with starvation are obliged to dig up cassava root crops in long-abandoned fields containing unexploded mines.