Officers in the field were well aware of the killing operations being conducted by the "Einsatzgruppen". The Wehrmacht tried to justify their considerable involvement in the "Einsatzgruppen" massacres as being anti-partisan operations rather than racist attacks, but Hillgruber wrote that this was just an excuse. He states that those German generals who claimed that the "Einsatzgruppen" were a necessary anti-partisan response were lying, and maintained that the slaughter of about 2.2 million defenceless civilians for reasons of racist ideology cannot be justified.