Do Mental Health Nurses have to go into the Battlefield?

In terms of deployments, as a mental health nurse, you will deploy to a field hospital. Field hospitals tend to be quite far away from any ongoing combat, so an injury due to trauma from combat is very unlikely. However, given the changing nature of combat, we can't say that you will never deploy somewhere that is potentially dangerous, hence all officers and soldiers, regardless of role, are trained in basic soldering skills, including how to use a weapon.

I would encourage you to start an application on the Army website, you will be able to discuss your aspirations with someone who knows more about the role of a mental health nurse and this should help you decide what you wish to do. https://apply.army.mod.uk/how-to-join