Not to defend any particular case but I think it is easy to see that there must have been a time when the volunteers had no idea what they were in for, and that

Not to defend any particular case but I think it is easy to see that there must have been a time when the volunteers had no idea what they were in for, and that after they were in too deep they might have feared for their lives. Many of them probably had no idea what atrocities were going on in the name of their country. So, I think you need to judge people on a case-by-case basis when it comes to alleged war crimes. The same goes for people who join political parties in countries where it is a virtual prerequisite to any kind of professional work. Not only may they be unaware of the bad deeds of the party, but they may have concluded that they could do nothing about the party's actions anyway.