In the same spirit, General Müller, who was the Wehrmacht's senior liaison officer for legal matters, in a lecture to military judges on June 11, 1941 advised the judges present that "...in the operation to come, feelings of justice must in certain situations give way to military exigencies and then revert to old habits of warfare ... One of the two adversaries must be finished off. Adherents of the hostile attitude are not to be conserved, but liquidated". General Müller declared that, in the war against the Soviet Union, any Soviet civilian who was felt to be hindering the German war effort was to be regarded as a "guerrilla" and shot on the spot. The Army's Chief of Staff, General Franz Halder, declared in a directive that in the event of guerrilla attacks, German troops were to impose "collective measures of force" by massacring villages.