How do you suppose soldiers could participate in such barbaric acts?

Barbaric acts of soldiers (mostly rape and murder of the civilian population) are never acceptable! But there might be a number of circumstances that might make it more probable that they happen. If soldiers have experienced a lot of brutality themselves, have been separated from their family for too long without any support, are unsure of their own life, and else have experienced a lot of stress, it might contribute to them not behaving like they normally would. Additionally, a group bonding might play a role (if they feel pressure to be accepted in the group of soldiers...)