 A series of nine separate field tests were conducted at the Chemical Corps Proving Ground, Dugway, Utah, to demonstrate and to evaluate the penetration of GB nerve gas into hard targets. Test animals whose resistance to GB is comparable to or slightly higher than man's were placed in targets of varying hardness. This included a sandbagged machine gun position, a two-man covered foxhole, a hasty fortification, and a concrete command post bunker. Almost 4,000 yards away, a battery of 155 mm howitzers prepared to fire standard GB-filled shells at the target complex. In command, all six pieces were fired. The visible cloud is burnt powder and dust kicked up by the bursting shells. GB itself is invisible in air. The howitzers were reloaded and fired as quickly as possible to put six more rounds on the target. Within 15 seconds, 75 pounds of GB had been dispersed. These scenes were filmed simultaneously by remote control cameras in each separate location and have been shortened to conserve the running time of the film. The animals in the machine gun position were the first to be affected. Although protected from blast and shell fragments, by the time the smoke and dust had cleared away, the pigeon in the foreground was dead from the effects of the nerve gas. Less than 40 seconds had elapsed. The pigeon in the two-man foxhole also has died in less than 40 seconds. The rabbit and goat showed symptoms in less than a minute and were dead in less than four minutes. The sampling equipment in each position measures the concentration of GB that penetrates the fortification. The animals in the hasty bunker began to react to the GB in less than two minutes and were dead within three minutes. The goat in the machine gun position has now expired. It is less than three minutes since the shells landed. The effects of the nerve gas on the two goats in the command post bunker were evident in less than two minutes. Fortified positions of this kind are so sturdy that anything less than direct hits with high explosive shells from medium artillery probably would fail to cause any casualties. None of the test animals were killed or even injured by blast or shell fragments. All the animals were killed by the toxic chemical within four minutes after the GB shells landed in the target area. It must be recognized, of course, that with troops occupying hard targets such as these, GB casualties would be minimized if the men were properly masked before the toxic cloud enveloped them. These tests demonstrated how quickly lethal concentrations of GB nerve gas can penetrate hard targets and fortifications of the type that normally provide considerable protection from high explosives.