In 1939, Hrabak was made a Staffelkapitän (squadron leader) and with Jagdgeschwader 76 (JG 76—76th Fighter Wing) participated in the Invasion of Poland and Battle of France and claimed his first aerial victory on 13 May 1940.

During the Wiederbewaffnung (rearmament) of West Germany, Hrabak joined the newly established German Air Force in 1955.

Following further command positions, Hrabak was named NATO's Chief of Air Defense/Central Europe until becoming special manager for the Lockheed F-104 Starfighter programme.

Hrabak was born on 19 December 1914 in Großdeuben, part of Böhlen, in the Kingdom of Saxony, a federated state of the German Empire, the son of a real estate developer.

[2] World War II in Europe began on Friday 1 September 1939 when German forces invaded Poland.

In preparation of the invasion, I. Gruppe of JG 76 had been moved to an airfield at Stubendorf, present-day Izbicko in Poland, in mid-August 1939 and supported the German advance on the central and southern sectors of the front.

[3] On 3 September, Hrabak made a forced landing behind enemy lines following combat with PZL.23 light bombers and returned to his unit the next day.

[7] During the Battle of Britain he added ten victories against Royal Air Force (RAF) fighters.

The presentation was made by Reichsmarschall Hermann Göring in his personal command train at Beauvais on 23 October.

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

[10] In early November, the Gruppe was withdrawn from the Eastern Front for a period of rest and replenishment where they were based at airfields in Döberitz, and later at Uetersen.

On 20 January 1942, the Gruppe began relocating to the Eastern Front where they would be based at Siverskaya near Leningrad.

At the time, JG 52 was based at Prokhladny and Gonschtakowka and operated over the front at the Terek River in the Northern Caucasus.

[15] On 23 November, the Geschwaderstab (headquarters unit) of JG 52 began its retreat from the Caucasus region and moved to Maykop.

While the Battle of Stalingrad was coming to end, Hrabak and the Geschwaderstab were ordered to Rostov-on-Don on 20 January 1943 to organize fighter protection over the retreating Army Group A.

He was the 337th member of the German armed forces to be so honored and at the time was credited with 118 aerial victories.

Also presented with awards that day by Hitler were Hauptmann Hans-Ulrich Rudel, who received the Swords to his Knight's Cross with Oak Leaves.

Rudel's air gunner and radio operator Oberfeldwebel (Master Sergeant) Erwin Hentschel was honored with the Knight's Cross.

In 1964, he was named NATO's Chief of Air Defense/Central Europe until becoming special manager for the Lockheed F-104 Starfighter programme.