For militarysoldiers, a tour of duty is usually a period of time spent in combat or in a hostile environment. In the Army, for instance, its active duty soldiers serve 24 hours a day, seven days a week for the length of their service commitment. Soldiers in World War Two were deployed for the entire war and could be gone for 4-5 years.
In World War II, Royal Air Force doctors had started to notice symptoms of battle fatigue in their pilots. Before 1942, there was no official limit for an operational tour. Some pilots had been flying over 200 missions with only a short break. Then the Senior Medical Officer of the RAF station Biggin Hill intervened, after asking one flight sergeant how many missions he had done and was surprised to hear 200 over 2 years. A tour system was then adopted, the length of it varied, depending on period, theatre, and Command requirements of the time. In (Western Europe), it was set at 200 hours operational flying. In 1944 in South East Asia, the day fighter pilot's tour was 300 hours or 12 months. In Bomber Command, the tour length was exceptionally based on the number of successful combat sorties (missions), the first tour was 30 sorties and the second 20 sorties. In Coastal Command, the maximum length of a tour depended on tasks and varied from fighter to squadrons, normally 200 hours for flying boats and four-engine land-plane crews’ 800 hours.
The tour of duty for B-52 crewmen is four to six months.