Frommherz began as a two-seater pilot with the ''
Luftstreitkräfte's
Kampfstaffel
(Tactical Bomber Squadron) 20 of Kagohl IV
, at the Battle of Verdun and over the Somme River. He was commissioned as a Leutnant on 1 August 1916. Kasta 20 then moved to serve in Romania in December 1916, before being posted onward to Macedonia and Thessaloniki, Greece. Frommherz scored his first victory on 11 April 1917 – a No 23 Squadron RFC SPAD VII – and a Royal Aircraft Factory BE 2e as his second on the 14th. and August, ten in September, four in October, and two on 4 November. Notable among his kills were the half dozen against the formidable Bristol F.2 Fighters. In the midst of his victory string, on 29 July 1918, he succeeded Hermann Göring as commanding officer of Jagdstaffel 27''. De Ridder left a description of Frommherz's
Fokker D.VII insignia. It consisted of the yellow nose and tail common to his Jasta, along with red and black chevrons of a
Staffelführer (squadron leader) painted on top of the upper wing. Frommherz's blooming career now garnered him the Knight's Cross with Swords of the
House Order of Hohenzollern on 30 September 1918, when his victory total stood at 26. The following month, he received the Knight's Cross of the Grand Duchy of Baden's
Karl Friedrich Military Merit Order. At some point, he had also been awarded the Knight's Cross of the
Military Order of Saint Henry from the Kingdom of Saxony. Frommherz was also nominated for the
Pour le Merite, having scored the required 20 victories; however, the award was still unapproved upon the Kaiser's abdication. Despite this non-award, Frommherz was seen wearing the decoration after the war; ==After World War I==