Under Diekmann's command, troops from the SS Division Das Reich killed 643 inhabitants in the village, most of whom were women and children.

He said he committed the war crime in retaliation for the killing of a fellow SS officer named Helmut Kämpfe by the French Resistance.

[2] On 1 April 1933, Diekmann joined the Nazi Party, one week after the Reichstag passed the Enabling Act of 1933, essentially granting Adolf Hitler dictatorial powers.

He then completed a course for platoon leaders at the Junker School's Dachau branch in August 1938 and was designated an SS-Untersturmführer, the most junior commissioned officer rank of the SS, in SS-Verfügungstruppe (SS-VT), a mechanized infantry unit at the disposal of the Führer.

[2] On 22 June 1941, Nazi Germany opened the Eastern Front by invading the Soviet Union in Operation Barbarossa.

Due to combat losses, Das Reich was pulled from the front lines and sent west to refit as a Panzergrenadier mechanized infantry division.

[2] In January 1944, the Das Reich division was sent to the southern French town of Montauban as a reserve unit, in preparation for the anticipated Allied invasion of occupied Europe.

[2] Following the Allied invasion of Normandy, the French resistance intensified its efforts to disrupt German communications and supply lines.

German military commanders like Diekmann who had seen service on the Eastern Front had become conditioned by the extraordinary brutality of anti-partisan measures there.

Diekmann, who was not wearing a helmet at the time of his death, was killed by shrapnel to his head from a British artillery shell.

On 12 January 1953, a military tribunal in Bordeaux heard the charges against the surviving 65 of the 200 or so SS men who had been involved in the Oradour-sur-Glane massacre.

[12] On 9 December 2014, the court dropped the case, citing a lack of any witness statements or reliable documentary evidence able to disprove the suspect's contention that he was not a part of the massacre.

[1] According to a 2014 interview, Diekmann's eldest son Rainer had heard from his maternal grandfather's wife that his father Adolf had done "something very serious over there [Oradour] during the war."