Why do war atrocities and massacres happen?

Why do stuff like the Rape of Nanjing, the My Lai Massacre occur? What were the soldiers' motivations? And why do they still happen today? Are they really so sick as to take joy in such brutality? This may sound naive but do some people really lack a conscience. And I can see the Taliban and al-Assad's... show more Why do stuff like the Rape of Nanjing, the My Lai Massacre occur? What were the soldiers' motivations? And why do they still happen today? Are they really so sick as to take joy in such brutality? This may sound naive but do some people really lack a conscience. And I can see the Taliban and al-Assad's government committing these acts, but even soldiers from more developed countries like the United States or Europe commit these war crimes from time to time. And didn't the warrior code of honor (taken from bushido) that the Japanese soldiers abided by say anything about how dishonorable it is to engage in rampant slaughter and rape?
6 answers 6