German Army ("Heer") officers, General Friedrich Olbricht, Major General Henning von Tresckow and Colonel Claus von Stauffenberg modified the plan with the intention of using it to take control of German cities, disarm the SS, and arrest the Nazi leadership once Hitler had been assassinated in the 20 July plot. Hitler's death (as opposed to his arrest) was required to free German soldiers from their oath of loyalty to him ("Reichswehreid"). After lengthy preparation, the plot was activated in 1944, but failed.