Operation ''Sandstone'' was the third Nuclear weapons test conducted by The United States of America. The series of tests were made in 1948 and concentrated on weapon design, rather than atomic effects (blast and radiation). The tests were conducted in The Pacific Proving Grounds (near Enewetak Atoll). The tests were also one of the first in which The US Armed Forces took a secondary role, allowing The Atomic Energy Commission full control.
A primary result in these tests were redevelopment of Bomb Cores, making them more efficient in design and detonation. These tests lead directly to The Mark 4 Device, which would remain a primary design for nearly 30 years. Over 10,000 civilian and military personnel took part in ''Sandstone''. (3) separate tests were conducted (Code Named: ''Sally'', ''Janet'' and ''Yvonne''). All tests were ground based (Tower), in which 49 Kilotons were detonated in total. As a result of ''Sandstone'' and the refining of Atomic weapons design, American would double it's overall weapons total to 169 devices by 1949.