Croneiss was one of the German pilots assigned to duty with Germany's allies, the Ottoman Empire.^[1] As such, he was assigned to Feldflieger Abteilung 6, which was also known as the Jasta Chanak Kale—Turkei as early as late 1915 or early 1916. His first aerial victory came on 7 January 1916, when he downed a Farman bomber over El Sedd-ul-Bahr. The next day, he downed a Royal Naval Air Service Voisin III LAS in the vicinity of Cape Helles. On 4 February 1916, his victory was over a reconnaissance two-seater at Baba-Tepe, off Imbros.^[1]

On 24 January 1918, Croneiss shot down a Sopwith over the Gulf of Saros. His fifth victory came on 23 May 1918, when he destroyed a Sopwith fighter. He was subsequently decorated with the Iron Cross First Class and the Knight's Cross of the House Order of Hohenzollern in August 1918.^[1][2]

Having survived the war as an Oberleutnant, Croneiss became a sporting aviator. He became director of a flying club that sponsored Willy Messerschmitt. Croneiss piloted one of Messerschmitt's early designs, the M-21, to win the designer a 60,000 Reichsmark prize. In 1928–1929, Croneiss won the East Prussia Flying Trophy with the M-23 model. He later evolved into a test pilot for the Messerschmitt Company.^[1]

Early in 1934 SA Chief Ernst Röhm 'had chosen Theo Croneiss to replace Hermann Göring as air minister, for example, and had given him a magnificent ceremonial dagger. Croneiss ratted Röhm out to Göring. Röhm denied it...Reichsführer Himmler rewarded Croneiss with high SS rank later.' Irving, David (2020). True Himmler. Focal Point. p. 256-257. ISBN 1 872 197 83 3.

Theodor Jacob Croneiss died on 7 November 1942.^[1]

• Iron Cross of 1914, 2nd class (2 January 1915) and 1st class (26 September 1916)
• Knight's Cross of the Royal House Order of Hohenzollern with Swords (6 August 1918)^[1]
• War Merit Cross, 2nd class (1942)
• Liyakat Medal
• Imtiyaz Medal
• Order of the Medjidieh
• Ottoman War Medal (Turkish: Harp Madalyası), "Gallipoli Star" or "Iron Crescent"^{[citation needed]}

• Franks, Norman; Bailey, Frank W.; Guest, Russell. Above the Lines: The Aces and Fighter Units of the German Air Service, Naval Air Service and Flanders Marine Corps, 1914–1918. Grub Street, 1993. ISBN 0-948817-73-9, ISBN 978-0-948817-73-1.