Original: Adolf Hitler , then a corporal in the German army , was ordered to spy on the DAP in September 12 , 1919 during one of its meetings at the Sterneckerbräu , a beer hall in the center of the city .
Simplified: When Adolf Hitler was still a corporal in the German army , he was ordered to spy on the DAP during one of its meetings at the Sterneckerbräu on 12 September 1919 .