Anton Ludwig Friedrich August Mackensen (6 December 1849 – 8 November 1945, ennobled as von Mackensen in 1899) was a German field marshal. He commanded successfully during the First World War of 1914–1918 and became one of the German Empire's most prominent and competent military leaders. After the armistice of November 1918 the victorious Allies interned Mackensen in Serbia for a year. He retired from the army in 1920; in 1933 Hermann Göring made him a Prussian state councillor. During the Nazi era (1933–1945), Mackensen remained a committed monarchist and sometimes appeared at official functions in his First World War uniform. Senior NSDAP members suspected him of disloyalty to the Third Reich, but nothing was proven against him.