The Brixental belonged to Salzburg until it fell to the newly established Kingdom of Bavaria in 1805; the Bavarian government left the castle ruin to the Itter citizens who used it as a quarry.

After the 1938 Anschluss annexation of Austria by Nazi Germany, the Reich government officially leased the castle in late 1940 from its owner, Franz Grüner.

[3] Itter Castle was seized from Grüner by SS Lieutenant General Oswald Pohl under the orders of Heinrich Himmler on February 7, 1943, and transformed into a prison by April 25, 1943.

Established to incarcerate prominent French prisoners valuable to Nazi Germany,[4][5] the facility was placed as a subcamp under the administration of the Dachau concentration camp.

Shortly after the SS-Totenkopfverbände guards fled, the prisoners armed themselves and awaited an anticipated attack from Waffen SS troops still aggressively resisting surrender.

The battle continued through the morning of 5 May, with a strong force of 100–150 SS pressing the attack until reinforcements from the American 142nd Infantry Regiment arrived around 4 PM that day.