He was killed in action following combat with Royal Air Force (RAF) Supermarine Spitfire fighters on 15 May 1943.

Hannig was born on 13 November 1921 in Frankenstein, present-day Ząbkowice Śląskie, at the time in Lower Silesia.

After he graduated with his Abitur (diploma), Hannig joined the military service in the Luftwaffe as a Fahnenjunker (officer cadet) in October 1939.

[6] The German invasion of Poland had begun on 1 September 1939, and marked the beginning of World War II in Europe.

[8] The Wehrmacht launched Operation Barbarossa, the invasion of the Soviet Union, on 22 June with II.

Gruppe flew multiple missions in support of German bombers attacking Soviet airfields near Kowno, present-day Kaunas.

Two days later they moved to Dünaburg, present-day Daugavpils, where Hannig claimed an Ilyushin DB-3 bomber shot down.

[10] On 17 July, for seven aerial victories to date, he was awarded the Iron Cross 2nd Class (Eisernes Kreuz zweiter Klasse).

[2] That day, the Gruppe moved to an airfield named Sarudinje located near Pleskov, present-day Pskov, southeast of Lake Peipus.

[16] In early November, the Gruppe was withdrawn from the Eastern Front for a period of rest and replenishment where they were based at airfields in Döberitz, and later at Uetersen.

[18] Flying missions over the Volkhov, Hannig claimed his first aerial victory in 1942 over an I-18 fighter on 5 February.

He and Leutnant Hans Beißwenger received the Knight's Cross from General der Flieger Helmuth Förster at Siverskaya.

[25][26] Following the Knight's Cross presentation, Hannig claimed his next aerial victory on 11 May when he shot down a Mikoyan-Gurevich MiG-3 fighter in the Demyansk combat area.

Hannig then claimed a Yak-1 fighter shot down near Zaluchye located approximately 40 kilometers (25 miles) west of Demyansk on 7 July.

[28] On 24 July, he claimed his 54th victory, an Ilyushin Il-2 ground-attack aircraft near Lychkovo located southeast of Lake Ilmen.

[33] On the morning of 2 September, Hannig and Unteroffizier Walter Heck claimed two Yak-1 fighters shot down, one each.

[Note 3] The pilots, Starshiy Leytenant Rubtsov survived the encounter with injuries while Serzhant Levinskiy was killed in action.

[37] On 28 September in aerial combat, Hannig flew his Bf 109 G-2 (Werknummer 10366—factory number) into the ground near Andronovo.

Staffel of JG 2, he claimed further eight aerial victories, including one four-engine United States Army Air Forces (USAAF) heavy bomber.

I. Gruppe claimed the destruction of five Boeing B-17 Flying Fortress bombers, including one shot down by Hannig northeast of Lannion.

Fighting this attack force, Hannig was credited with the destruction of a Spitfire shot down northeast of Cherbourg.

Defending against this attack, elements of I. Gruppe intercepted the RAF fighters and claimed four aerial victories, two of which were not confirmed.

Hannig was credited with the destruction of a Spitfire shot down east of Troarn, his 98th aerial victory.

[42] In this engagement JG 3 lost four aircraft with three pilots killed in action, including Hannig.