April 1943 brought organisational changes. JG 1s four "gruppen" were separated to form two two-"Gruppe" wings—JG 1 and JG 11 on 1 April. Each had to establish a III. "Gruppe". JG 1s was activated at Leeuwarden on 23 May. Karl-Heinz Leesmann became the commanding officer until his death on 25 July. Hans Philipp took command of JG 1 on the same date, while I. "Gruppe" was moved to Deelen. JG 11 picked up III./JG 1 I./JG 11 at Husum and I./JG 1 II./JG 11) at Jever. JG 11 took over the defence of southern Norway, Denmark and the northernmost part of the German North Sea coast. JG 11 reported to "Jafü Deutsche Bucht" but formed part of "Jagddivision" 2. JG 1 retained IV. "Gruppe" [renamed I. "Gruppe" at Deelen and II./JG 1 at Woensdrecht, reporting to "Jafü-Holland-Ruhr" in "Jagddivison" 1. JG 1 was now responsible for covering only half of its old sector.