There are a great many things which adversely affect the soldier in battle. If he does not eat regularly, his general fitness will quickly suffer. If he does not sleep sufficiently, his powers of concentration will diminish. If he gets too wet, he may catch a cold. These facts will be realized by the soldier only gradually, and they will not begin to worry him until his general condition has deteriorated considerably. If these or similar circumstances begin to worry him, then, in the context of this study, he is suffering from stress.