Aviation in World War II were struggling to re-equip with similarly modern types and to train up aircrew. Early German successes, with the notable assistance of the Junkers Ju 87 "Stuka" dive-bomber, overran Europe and left Britain open to attack. During the ensuing Battle of Britain, the British fighter squadrons had to quickly relearn the old tactical lessons from the first war. Initially the RAF fighters flew in a tight three-fighter arrowhead formation, soon changing to the looser four-aircraft arrangement which the Germans called the "finger-four." They soon also relearned the value of climbing above your opponent before attacking. At the same time, the development
Junkers J 2 earlier J 1's structure. Junkers began wind tunnel and design work promptly upon receipt of the contract, and by the end of the spring of 1916 the first example was completed. The J 2 differed from the J 1 in having a cowling that almost entirely enclosed the engine, a rounded upper and lower fuselage section instead of the rectangular section of the J 1., and a narrower and deeper ventral radiator enclosure, and had a horizontal stabilizer planform shape that would become familiar on later, all-duralumin Junkers monoplane designs to be built during 1917-18. The "all-moving" rudder still possessed