Operation Desert Rock was a series of seven tests between 1951-1957 where troops were involved in exercises near nuclear test explosions. The goal was, in part, to see how the psychological effect of seeing a nuclear blast affected the troops themselves. The fear was that upon being subject to a nearby nuclear attack, the troops would go into a state of shell shock and be unable to function, unable to obey orders. (There were reports during World War II of very heavy bombs rendering German troops into such a state.)

As for the dangers, the main health problem is that at this point they still did not have a great understanding of the blast wave physics for the range of the blasts here. Under a strictly theoretical model, the troops would have been fine: the prompt (immediate) radiation from a nuclear test is only intense in an area just around ground zero, and so if troops were in that area they would already have been fried by heat or blast; the residual radiation (fallout) is theoretically predictable, monitor-able, and travels with the wind.

In practice, nature is more complicated than this, and many of the soldiers were in an area where they were exposed to radioactive debris. Their understanding of how to decontaminate from it was rudimentary. Additionally, scientific understanding of the dangers of even low levels of radiation, applied across large numbers of people, changed dramatically in the era after atmospheric testing stopped. Their exposures were not so high as to produce immediate, acute effects (e.g. radiation poisoning), but were high enough to produce long-term effects spread out statistically over their whole population. These soldiers are known technically as "atomic veterans" and there have been efforts to get compensation for those who later came down with illnesses associated with radioactive exposure.