Shell shock is the reaction of some soldiers to the trauma of battle. During the War, the concept of shell shock was ill-defined. Cases of "shell shock" could be interpreted as either a physical or psychological injury, or simply as a lack of moral fibre. Soldiers could for example not be able to hear or see anything for a short period of time, as well as no longer feel pain (Analgesia). After the second World War the 'Shell shock' term was replaced by "Combat stress reaction'.