The history of the W48 began in April 1954 when the US Army expressed interest in a small low-yield nuclear projectile. The initial development was the W33 gun-type projectile but the Army was interested in an improved or and even smaller diameter weapon. A study was commissioned to explore the development of a small-diameter implosion type artillery shell. The technology at this time was not sufficiently advanced to develop such a weapon but significant progress was made by the University of California Radiation Laboratory (UCRL) over the next twelve months. A further study of an implosion weapon was also commissioned that lead to initial work on the XW48 focused on the design, leading to the cancellation of the XW32 shell in favour of the WX48 in May 1955. Although the details of the study are classified, the results were positive enough that by September 1956 that emphasis moved to developing a 155 mm shell.