combat means such as raids and ambushes. They can also use methods less risky to their security, such as mining or long-range sniping. Raids and ambushes Raids are short-duration attacks on objectives, with the specific understanding that the attacking force will withdraw quickly after achieving the mission objective, or finding they are confronting forces too strong to handle. UW raids can be simply to disrupt an enemy force, to capture usable equipment, for taking prisoners for intelligence exploitation, and destroying installations. Both for attacking strong points at a distance, and for destroying reinforced structures, SF may use missiles, typically derived from antitank weapons. When the raiding force can access the key target, they often use explosives, manually placed so that a small amount can do maximum damage. Certain targets, such as bridges, historically could be attacked only by manually placed explosives. With the advent of precision-guided munitions, the destructive part of the raid may involve the SF unit controlling air strikes. Air strikes, however, are practical only when U.S. involvement is not hidden. Where a raid goes to the enemy and attacks, an ambush waits for enemy forces to come to it, and then engages in combat. A well-planned ambush can have the element of surprise, possibly achieve temporary local superiority, fight from cover, and have preplanned withdrawal routes to avoid being encircled. Mining and sniping support both raids and ambushes. In a raid, mines may be laid near the enemy reaction force barracks. Snipers can take out critical equipment (e.g., floodlights, radars, artillery) or commanders as the raid begins. Both methods can discourage pursuit while the raid or ambush force withdraws. Mining and improvised explosive devices In guerrilla warfare, a great number of casualties are caused by mines and other destructive devices that are triggered by some mechanical interaction between a person and the detonation mechanism of the device. Since such devices rarely have a means of distinguishing between a combatant and a noncombatant, there is a very real risk to civilians, and continues to be in areas of the world where there has been much guerrilla warfare. The United States has not ratified the 1997 Convention on the Prohibition of the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on their Destruction, known informally as the Ottawa Treaty. It does promulgate policies and Rules of Engagement for their use. When an explosive device is triggered only by