S.L.A. "Slam" Marshall was a veteran of World War I and a combat historian during World War II. He startled the military and civilian world in 1947 by announcing that, in an average infantry company, no more than one in four soldiers actually fired their weapons while in contact with the enemy. His contention was based on interviews he conducted immediately after combat in both the European and Pacific theaters of World War II.

To remedy the gunfire imbalance he proposed changes to infantry training designed to ensure that American soldiers in future wars brought more fire upon the enemy. His studies during the Korean War showed that the ratio of fire and more than doubled since World War II.