Early trauma can be a big problem for them, considering experiencing something like war can be life altering. Most kids who are in a war zone or have dealt with war, have a lot of mental health problems because of it. They may have things like paranoia, extreme anxiety and stress, being unable to cope, being desensitized to war and brutality, and so on.
I think the first thing that needs to be done for these children, is to get them support asap. Find them therapists and doctors that can help. If that's not possible, trying to make their lives better can go a long way. But of course, that's not always possible when in a time of war. Some kids likely won't find the support they need and may have to get through it by themselves or with support from family and friends. But when in a war torn area, it's a lot easier said than done.