Dismayed by the atrocities committed by the Ustaše, he was involved in the Lorković-Vokić plot, with the purpose of overthrowing Ante Pavelić's regime and replacing it with a pro-Allied government.

Originally a monarchist, Glaise-Horstenau became the second man in the hierarchy of the banned Austrian Nazi Party in the mid-to-late 1930s behind its leader Josef Leopold.

Ad hoc intervention in individual cases could make the German Army look responsible for countless crimes which it could not prevent in the past.

[6]The lack of response from the OKW at Glaise-Horstenau's criticism of the Ustaše's methods increasingly frustrated him and caused deep tension with Ante Pavelić, the poglavnik, or head, of the Independent State of Croatia.

By 1944, he had grown so dismayed at the atrocities that he had witnessed that he became deeply implicated in the Lorković-Vokić plot to overthrow Pavelić's regime and to replace it with a pro-Allied government.