Promoted to Hauptmann in 1913, Hühnlein served in World War I, as a company and battalion commander, obtaining the rank of Major.

He later described Hitler's effect on him thusly: I was possessed by his philosophical outlook on the world, it drew me to him, held me fast, and inspired that sort of disciplineship which only ends with death.

[4]By 1923, he was a member of both the Sturmabteilung (SA), and Ernst Röhm's short-lived anti-Semitic nationalist Bund Reichskriegsflagge (Imperial War Flag Society).

[4] He participated in the Beer Hall Putsch, the unsuccessful attempt by Hitler and the Nazi Party to seize power in Munich on 9 November 1923, for which he would be awarded the Blood Order.

That year, he joined the Nazi Party (membership number 375,705) and rejoined the SA, serving on the staff of its supreme command (Obersten Führung).

[7] After the Nazi seizure of power at the end of January 1933, Hühnlein on 5 March was elected to the Reichstag as a deputy from electoral constituency 31, Württemberg.

On 2 September 1934, some two months after Röhm's death in the Night of the Long Knives, the NSKK was made an independent organization, free from SA oversight.

[8] Under Hühnlein's leadership, the NSKK membership rose rapidly, from 30,000 men in April 1933 to 350,000 in September 1933, after absorbing all of Germany's private motor clubs.

Hühnlein often presented the trophies at German Grand Prix races and made certain that Nazi flags and bunting covered the victory tribunes.

The most famous race car driver that had to answer to Hühnlein was Bernd Rosemeyer, who drove the Auto Union Silver Arrow.