What is "a-ration"

A-ration is a term used in the United States armed forces for a meal provided to troops which is prepared using fresh, refrigerated, or frozen foods. The use of fresh, refrigerated or frozen foods distinguish 'A' rations from 'B' rations, which use canned or preserved ingredients to enable them to be served without adequate refrigeration or freezer facilities. 'A' ration meals may be served in dining facilities ("DFAC"), prepared in the field by the use of field kitchens, or prepared at a fixed facility and transported to field locations in containers.