In July 1944, Claus von Stauffenberg attempted to assassinate Adolf Hitler with a bomb at his headquarters in Rastenburg, but Hitler escaped death. Instead of putting an end to the violence, Hitler ordered the execution of all German soldiers involved in the plot to overthrow him.... without a trial. Without a trial and the presentation of evidence, how did they know if these men were actually involved in the plot?

Sources:
https://en.wikipedia.org/wiki/20_July_plot

https://ceb.wikipedia.org/wiki/Adolf_Hitler#Kaparotan