The determination of mission count or tour length was approved at a higher level than the air group, and increased or decreased based on the requirements of the specific theater or course of the war.
The first system of "combat tours" for Army Air Forces personnel was implemented in July 1942 and lasted until about May 1943. The "one year tour" system resulted in many cases of combat fatigue due to varying mission loads, and Lieutenant General George Kenney, the commander of Allied Air Forces in the Southwest Pacific Area as well as the Fifth Air Force, also found that it resulted in shortages of replacement crews as too many men were becoming eligible to be sent home. In November 1942, Major General James "Jimmy" Doolittle established 25-30 missions or 150-200 flight hours as the goal for his Twelfth Air Force pilots in North Africa. Doolittle consulted with Major General Carl Spaatz (at the time, the overall commander of Army Air Forces operations in Europe and the Eighth Air Force) and Brigadier General Ira C. Eaker (at the time, the commander of VIII Bomber Command, Eighth Air Force), and they agreed upon the former's scheme for initial use in Europe. Brigadier General Nathaniel F. Twining, the commander of the Thirteenth Air Force in the Pacific, instead adopted a "points" system in January 1943 for his fighter and bomber pilots that took into account the number of months overseas, the number of flight hours, and the number of individual missions flown.
From May 1943 to January 1944, commanders in theaters (that is, the commanders of numbered Air Forces and higher organizations) were given exclusive jurisdiction by the War Department over the number of missions their crews flew before getting leave or returning home. When General Spaatz assumed command of the Northwest African Air Forces, he proceeded to limit his medium and heavy bomber crewmen to 150-250 flight hours (respectively) or 50 missions, after which their combat effectiveness would be assessed. Major General Lewis H. Brereton, the new commander of the Ninth Air Force (re-established in England in October 1943), set 50 missions as the tour of duty for his medium bomber pilots, and 200 flight hours for his fighter pilots.
As Luftwaffe opposition was gradually forced out of the sky over western Europe in the several months before D-Day (a necessary component for a successful invasion) due to an ever-increasing number of aircraft (maximum capacity in England was reached in May 1944; 82 units at 86 stations, including 66 airfields) and the aggressive policy of new Eighth Air Force commander James Doolittle (if it flies, kill it; if it doesn't fly, find where it sits and kill it), the Army Air Forces adopted a policy of "maximum service;"
The Commanding General of the AAF directed the commanders to do two things. First, "If you have made any policies or understandings that combat personnel will be returned to the United States after fulfilling such arbitrary conditions as I have just described, those policies will be rescinded at once." Second, the impression that no man would be required to serve more than one tour in combat was to be "unmistakably corrected." While Arnold recognized that "this radical change in personnel policy will present difficult problems, particularly insofar as morale is concerned," he had "absolute faith...in the intelligence and good, hard, common sense of the American fighting men in understanding the necessity for the change and accepting it." He was counting on the commanders "to put it over."
Commanders in theaters responded by de-empahasizing the coveted "mission yardstick." Doolittle cancelled Eaker's 25-30 mission/150-200 hour program when he gained command in January 1944, and Brereton rescinded his 50 mission/200 hour scheme. The former offered 30 missions as a minimum, and later promised his men that they would be rotated home "when the efficiency of the unit was affected," and that no man would have to fly more than 35 missions. This program resulted in much grumbling, and several flyers threatened to quit. General Eaker was also displeased;
...The thing that makes it most difficult to maintain morale is to have no policy, leaving clearly in the mind of the combat crewman the belief that he must go on until he cracks up and becomes a jibbering idiot or an admitted coward, or until he is killed. We are all of one mind that the effectiveness of tactical units cannot be maintained under this condition.
From February to September 1944, Army Air Forces commanders in Europe experimented with a leave program, offering either noncombat duty in the theater or a 30-day furlough in the United States, in addition to the prospect of permanent rotation. By September, it was recognized that the program was a failure; many men who were eligible for temporary return to the United States wished to stay there, or were "burned out" and unsuitable for any further combat duty. The implied tour length before relief for Eighth Air Force heavy bomber crews was formally increased to 30 missions on April 1, 1944, and then 35 missions on June 6, 1944. In July 1944, the U.S. Seventh Air Force in the Pacific adopted a 30-mission yardstick for its heavy bomber pilots.
With the failure of the leave program, the Eighth Air Force went back to a policy of returning crewmen home when they began to become fatigued; oftentimes this happened before 30 or 35 missions. As the pace of operations in the Pacific increased, so did the number of required missions; in October 1944 in the Seventh Air Force, 40 missions in a heavy bomber, 60 missions in a medium bomber, and an eight-month tour for fighter and photoreconnaissance pilots. Similar to the Thirteenth Air Force, the Fifth Air Force adopted a points system to determine eligibility for rotation in September 1944.
Throughout the war, there was no protracted shortage of new crews to take the place of those lost through combat or fatigue, although the throughput process sometimes caused problems, especially with Fifth Air Force early in the war. The Army Air Forces suspended completely the procurement of new aviation cadets from March to November 1944 after a wildly successful recruiting drive in the last five months of 1943 and first three months of 1944.
This glut of replacements along with declining enemy resistance allowed for greater flexibility in rotation beginning in September 1944, and the Eighth Air Force proceeded to delete all references to tour length or mission requirements in the fall of 1944, relying only on fatigue and unit effectiveness to determine when a man should be relieved. In September 1944, the Twelfth and Fifteenth Air Forces in the Mediterranean Theater adopted the following informal tour lengths for their crews, which didn't differ much from those in effect before;
Heavy bomber, photoreconnaissance, and and weather aircraft, 50 sorties;
Long range fighters, 70 sorties;
Short-range fighters, 100 sorties.
Between September 1944 and April 1945, bomber crews of the Eighth Air Force averaged 35 missions, while fighter pilots flew about 270 hours prior to rotation.
Between November 1944 and May 1945, bomber crews of Ninth Air Force averaged 65 missions, and fighter pilots 150-200 hours.
I talk more about the situation in Europe regarding missions in this post here, as well as the conditions in one particular German prisoner of war camp for downed airmen, but I'll repeat my comments below.
As German fighter opposition decreased throughout early 1944, the threshold to return home was increased from 25 to 30, and then 35 missions;
Date|Bomber Crewmen (1)|Fighter Crewmen (2)|Photo Recon (2)|Weather Recon (2) :--|:--|:--|:--|:-- Prior to 01 Apr 1944|25 Missions|--|--|-- 01 Apr to 06 Jun 1944|30 Missions (A)|200 hours|--|-- After 06 Jun 1944|35 Missions (B)|300 hours|200 hours|500 hours
- Credited Combat Missions
- Operational Combat Hours
A. For those who had completed [at least] 15 missions, a sliding scale applied for the five additional missions. The nearer to 25, the fewer extra missions were required.
B. Lead and Deputy Lead Crewmen were given a reduction in the number of required missions depending on the number of Lead and Deputy Lead missions flown, subject to a minimum of 30 missions.
Crews that had flown a certain number of lead or deputy lead positions in formations were credited with additional missions on a sliding scale when the new system was fully implemented.
| Number of Leads | Number of Deputy Leads | Mission Reduction | Required Missions |
|---|---|---|---|
| 2 | 4 | none | 35 |
| 3 | 6 | 1 | 34 |
| 4 | 8 | 2 | 33 |
| 5 | 10 | 3 | 32 |
| 6 | 12 | 4 | 31 |
| 7 | 14 | 5 | 30 |
A combination of Lead and Deputy Lead Missions were given pro rata credit by converting Deputy Leads to Leads on the basis of 2 to 1. An odd number of Deputy Lead Missions was reduced to the even number below it.
Also due to the lack of German fighter opposition, one waist gunner was dropped beginning in June 1944, the other gunner in February 1945.
Sources:
Combat Crew Rotation: World War II and Korean War, by the Historical Studies Branch of the United States Air Force Historical Division
Craven, Wesley F., and James L. Cate, ed. The Army Air Forces in World War II, Volume VI: Men and Planes. Chicago: University of Chicago Press, 1955.
Heller based Catch-22 on his own experiences and that did include a lengthening tour of duty, though it was dictated at an air force level rather than by a particularly ambitious Colonel.
The USAAF did not start the war with a concept of a fixed duration of operations, but combat fatigue ("the physical or mental tiredness or disorder resulting from the stains and stress of combat") made it necessary to rest and rotate aircrew. The first proposal was for a one-year tour, but recognising that different circumstances applied in different areas of operation the policy was delegated to theater commanders in 1943. Theater commanders had to consider numerous factors, most notably casualty rates and availability of replacements, so policies varied; for heavy bomber crew of the 8th Air Force it was 25 missions (famously showcased by Memphis Belle), though when average losses on a raid were running at 5% that still meant poor odds on completing a tour. In the 12th Air Force, with lower loss rates and without sufficient replacements for 25 mission tours, a normal tour for medium bomber crew was 50 missions and 150 hours.
In 1944 General Arnold, wishing to build up the combat strength of the USAAF, was concerned over the idea that crew were fixated on a "contract" of being finished with combat after a fixed number of missions, and wrote to theater commanders stressing that rotation had to be more flexible, based on the conditions of individuals rather than fixed numbers of hours or missions, and "If you have made any policies or understandings that combat personnel will be returned to the United States after fulfilling such arbitrary conditions [...] these policies will be rescinded at once."
This did not meet with the approval of aircrew or some of their leaders; General Eaker of the Mediterranean Allied Air Forces complied, but warned that "The thing that makes it most difficult to maintain morale is to have no policy, leaving clearly in the mind of the combat crewman the belief that he must go on until he cracks up and becomes a jibbering idiot or an admitted coward, or until he is killed". Policy continued to vary between theaters, numbers of sorties were used as a guideline rather than fixed terms.
Joseph Heller served in the 488th Bombardment Squadron of the 340th Bombardment Group of the 12th Air Force, and the experiences of himself and others in the group are quite apparent in Catch-22. Jack Marsh was assigned to the group in 1942 and initially advised that a tour would be 25 missions; he was the first to complete 25, then 35, then 50 missions, told each time that the minimum number of missions had increased; waiting to return to the US after his 50th mission he voluntarily flew a 51st, which became a 52nd when the aircraft were refuelled and rearmed for an immediate second sortie. By the time Heller arrived in May 1944 the fifty mission target had been extended, as can be seen in [the diaries of the Group] (http://57thbombwing.com/340th_History/340thGroupHistory.php):
340th Group Diary, November 25, 1943
"He [Colonel Tokaz, the group commander] is instituting a new policy regarding the tour of duty of
combat crew personnel. In the past he has been recommending all men who have completed 50
missions to be returned to the zone of interior, the United States. Now he announces that due to the
almost complete lack of replacement crews he will try to extend the tour of duty past 50 mission where
ever he can. This will necessitate a check by the surgeon when a man has completed that number. If
the surgeon thinks he can fly more missions without returning home he will continue to fly in combat.
If not, he will be recommended for return to the States."
489th Squadron Diary, January 14, 1944
"S/Sgt. O'Connell reached the 50 mark today. The combat tour of duty no longer is set at 50 missions
but now depends entirely upon physical conditions."
340th Group Diary, August 20, 1944
"Something entirely new in the way of disciplinary problems cropped up today. The up-cropping is the
result of the recent order of this Wing that the men are to fly till they can fly no more. So many of the
men having come into combat with a seeming understanding that at fifty they would be entitled to
furloughs or rotation back to the States, and later to have the ante raised to 53 and now raised
indefinitely find themselves grumbling quite loudly. On the morning of the completion of their 55th
mission two gunners and several officers turned to the Squadron C.O. telling him that they thought they
had had enough flying and hoped to be taken off combat status. The two gunners are now in the guard
house under charges of misbehaving before the enemy. Actually all that was involved was their telling
the C.O. their intentions to no longer fly. It is apparent that the Group Commander and Wing
Commander are both interested in having the charges pressed if for no other purpose than to have a test
case upon which to base further action. Other combat members of the Group have grievously resented
this reaction of the Colonel and have lost much of the respect previously held toward him. The matter
is now under investigation......"
487th Squadron Diary, November 7, 1944
"It's quite evident that combat men who up to now
thought they were finished will have to fly at least ten more missions. After being threatened with
court-martial and the prospect of losing their rank the boys have decided to give in. Thus the quota of a
combat tour has increased to seventy missions which is probably exactly what was strived for when the
fracas started....."
Heller flew 60 missions, not far off Yossarian's 71, before returning to the US; others in the 340th clocked up over 100.
See:
"Joseph Heller's Combat Experiences in Catch-22", Michael C. Scoggins
"Combat Crew Rotation: World War II and Korean War", Historical Studies Branch, USAF Historical Division
"The True Story of Catch 22: The Real Men and Missions of Joseph Heller's 340th Bomb Group in World War II", Patricia Chapman Meder