This commonly occurs early during combat after as little as 24 hours of intense stress and sleeplessness. The body abruptly stops producing the high levels of adrenaline needed to sustain the initial activity. The result can be severe drowsiness, leading to near unconsciousness. Soldiers that are alert and aroused for 24 hours during the marshaling, loading, and insertion phase of an operation can be overcome by intense fatigue, which starts after dawn of the first day of combat. This effect can only be overcome by good leadership, motivation, and rest.
Extensive training delays the degradation of a task caused from lack of sleep.
Training does not prevent lack of sleep from eventually affecting the performance of a task, but repetitive, stressful, realistic training can delay and moderate these effects. Good physical training prepares the soldier for sustained operations. It also allows him to recover quicker after a short rest than a soldier who is in poor physical condition. A good diet and healthful lifestyle prepares the soldier to cope with the physical stress of sustained operations. Extensive Army studies on the effects of sustained operations on combat effectiveness show that the performance in all duty positions does not degrade the same.