A member of the Einsatzgruppen - a Nazi death squad that carried out mass executions - prepares to shoot a prisoner in the back of the head in Ukraine during the Second World War

A member of the Einsatzgruppen - a Nazi death squad that carried out mass executions - prepares to shoot a prisoner in the back of the head in Ukraine during the Second World War

'After a close analysis of these soldiers, I have identified five principle factors that had the greatest influence, either directly or indirectly, on the many members.'

Zapotoczny said that examining such factors may help to predict the actions of others in the future should similar circumstances arise. 

'The idea for this book sprang from my graduate thesis, which examined the actions of the Japanese Army and the actions of the German Einsatzgruppen during World War II.

'Together, the factors supported each other and crystallised into a modus operandi that resulted in atrocities and bestial acts on civilians. The soldiers who committed atrocities became violent criminals.

Photos depicting abuse at Abu Ghraib began to emerge in 2004, with some detainees claiming to have endured physical and sexual abuse, electric shocks and mock executions 

The images have been released in the book, Beyond Duty: The Reasons Some Soldiers Commit Atrocities by Walter S. Zapotoczny Jr, published by Fonthill Media. A Second World War picture in the book shows soldiers and civilians moving through Berlin, Germany

'While these are different situations in many ways, there are similar factors that allowed most of the soldiers in these groups to abuse or kill men, women, and children in cold blood,' he added.

'Historians, in large part, have described in great detail the actions of these groups, but they have not adequately dealt with the factors that contributed to those actions.'