Flashbacks are vivid visual memories. Most of my flashbacks are triggered by the smell of burning leaves and wood. Artillery rounds, bombs, and search and destroy missions all caused fires in Vietnam. So did helicopters and planes that were shot down. It seemed like everyday in Vietnam I saw at least one of the above happening.
Nightmares are just that, nightmares.
Once again they are so vivid that I wake up having a panic attacks. It is just like it is happening now. Voices, smells, tastes and sites all just rushing up to smack you in the head. Panic attacks happen not only from nightmares but are brought on by stress. Anger being the key emotion causes stress and stress causes anger.