The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

there, Hajo began his flying missions, ferrying Moroccan troops to and fro
between North Africa and southern Spain. Republican warships would open
fire from the Straits of Gibraltar and, once, Hajo’s plane was hit. From then
on, he would load lumps of stone and iron into the hold and would have
them dropped on the ships below as they flew over. Later, he was given real
bombs.
Help to Spain had initially been given in return for much-needed raw
materials, particularly iron and tungsten, yet it also allowed the German
pilots and aircrews to gain invaluable experience of flying in a combat
situation and for the Luftwaffe to test and develop its aircraft and tactics.
Some 15,000 pilots and crews would see service in Spain, and after its
highly secret beginnings Luftwaffe involvement in the Spanish Civil War
became more open with the creation of the Condor Legion in November
1936, although, to maintain the fiction of legality, all German members of
the legion were ‘volunteers’ and arrived in Spain wearing civilian clothes as
‘tourists’. Hajo was still there at that time. He finally returned to Germany
in April 1937, having massively increased his flying hours and with it his
experience. He had learned many important lessons during that time.
So too had the fighter pilots, who had begun their time in Spain with
Heinkel 51 biplanes but had progressed on to the new Messerschmitt 109B
and later Cs. These fighter pilots had soon learned that the best flying
formation was not the tight three-plane vic as had been practised in the last
war, but a two- or four-aircraft formation, with two Rotten together making
a Schwarm. Experience proved that a formation could be most effective
when spaced apart with about 600 feet between each aircraft; it ensured the
lead aircraft could be protected by his wingman, but also meant that from a
distance the formation was harder for the enemy to spot than a group of
tight formation fighters. The extra space also gave them greater freedom to
manoeuvre. It was Werner Mölders, commander of the fighter unit 3/J88,
who did much to refine these fighter tactics, introducing the idea of
staggering the two pairs of a Schwarm: the Schwarm leader flew in the
position of the tip of the middle finger, his wingman in that of the index
finger; the second Rotte leader was represented by the third finger, and his
wingman by the little finger – hence it became known as the ‘finger-four’.
He also introduced the cross-over turn, a manoeuvre the RAF had
developed at the end of the last war. This got around the problem of trying
to turn when the frontage of a Schwarm was some 600 yards: to turn