Why were prisoners marched from Bataan to San Fernando?

The prisoners were marched from the Bataan Peninsula to San Fernando because the Japanese military intended to transport them by rail to Camp O’Donnell, a former Philippine army training center used for internment.1

Following the surrender of Allied forces on April 9, 1942, the Japanese military found itself logistically and materially unprepared for the unexpectedly large number of captives—approximately 76,000 Filipino and American troops. To manage these prisoners, the Japanese ordered them to the east coast of the Bataan Peninsula, where they were organized into columns and forced to march north to the railhead at San Fernando. From there, the captives were packed into cramped, unsanitary boxcars to continue their journey toward the prison camp.1