Why were prisoners crowded into boxcars at San Fernando?

The Japanese military crowded prisoners into boxcars at San Fernando because they had severely underestimated the number of captives they would take and were logistically unprepared to transport them.1

As a result, they forced as many as 100 or more men into small, prewar boxcars that were designed to hold only 40 people. This overcrowding, combined with the lack of ventilation in the ovenlike conditions of the cars, resulted in hundreds of prisoners dying while standing up during the journey to Capas. The brutal treatment of these prisoners of war, who were viewed by their captors as little more than chattel, stands as a profound violation of the fundamental human rights and dignity that must be afforded to all individuals, regardless of their status in conflict.1