A medal winning low-level photographic intelligence flight on 13 March 1915 under heavy fire was pivotal in getting him a fighter posting.

Müller's victory toll rose to second among German aces, trailing only Manfred von Richthofen, the Red Baron.

His native Bavaria decided he deserved its equivalent national award, the Military Order of Max Joseph.

On 9 January 1918, Müller's Albatros airplane was set on fire by a British reconnaissance plane he was attacking.

[2][3] The Minister having been persuaded, Müller was posted to the army flying school at Schleißheim on 1 December 1913, and after four months of training he became a fully qualified pilot on 4 April 1914.

Already noted as an aggressive and skilled airman, Müller was one of the first pilots to fly the Fokker Eindecker in action.

45 Squadron RFC Sopwith 1 1/2 Strutter of Captain William Wright, who survived; it was Müller's seventh win.

[8] On 28 July, he shot up the Sopwith 1½ Strutter of Captain Matthew Brown Frew and gunner Lieutenant George Al Brooke.

A year after Müller had joined Jagdstaffel 2, he had gotten an impressive score of 27 victories and been awarded the Pour le Merite on 3 September 1917.

[8] With the many medals that had been awarded to him, he was one of the most highly decorated aces in the entire German air service, second only to Manfred von Richthofen[3] However, by October, Müller was at odds with his commanding officer, Emil Thuy, and desired a change.

[10] With the death of his friend Heinrich Gontermann in late October, Müller was second only to Manfred von Richthofen as the highest scoring ace still at the front.

[8] Müller wangled a transfer back to Jagdstaffel 2 on 3 November 1917, rejoining his old friend, commanding officer Erwin Böhme.

[13] When the Jagdstaffel 2 leader, Walter von Bülow-Bothkamp, was killed on 6 January, Müller temporarily inherited the command of the Jasta.

A letter by his squadronmate Leutnant von Gudenberg told the tale:[15] "The Kette (Flight) together attacked an RE two-seater.

[17] After the war, in early 1919, Müller was finally approved for the Knight's Cross of the Military Order of Max Joseph, backdated to 11 November 1917.