Only 34 years old at the end of the war, he held the rank of SS-Brigadeführer and generalmajor of the Waffen SS and was a recipient of the Knight's Cross with Oak Leaves.

Stadler was born in Austria, the son of a Styrian miner, who learned the profession of electrical engineer after elementary and state school in Judenburg but joined the Nazi party and the SS in May 1933.

From March 1, 1942 he commanded the 2nd Battalion of the Panzer Grenadier Regiment Der Führer belonging to the SS Division Das Reich.

To recuperate, the Der Führer regiment, which had been severely decimated in Russia, was relocated to France in the Toulouse area at the beginning of 1944 - just like the remaining 2nd SS Panzer Division “Das Reich”.

On 10 July 1944, Stadler was appointed commander of the SS Division Hohenstaufen; it fought on the Eastern Front, in Normandy, at the Falaise pocket, at Arnhem ("Operation Market Garden"), in the Ardennes offensive and in Hungary.