I’ll define trauma as a fight, flight or freeze (and disassociate) reaction to a subjectively percieved threatening situation.
This trauma is stored in the bodymind from the moment the reaction took place. Well known Trauma therapist Peter Levine says that the issue is not the fight, flight or freeze reaction in itself, but that we don’t allow our bodies or are not able to allow the body to process the trauma.
Collective trauma was for example inflicted during the second world war:
A collective of individuals believing to be separate and superior invaded their neighboring country violently, which threatened the indvidual and collective idea of a separate self of the neighbor. In this case a collective of indivduals was traumatized in a similar way.
At the Vlierhof the now 82 year old founder had experienced the invasion of the Netherlands by the Germans, which had inflicted a trauma, which led to founder recreating a situation in which he believed the Germans were invading his community. It was not only the founder believing this to be true since this was a collective trauma, yet everyone else identifying as Dutch in the community. The founders trauma triggered the trauma of his collective and colored their perception.
I came to the Vlierhof, which was located in Germany, and thought it was only fair that Germans could work there, and I saw how those identifying as German were oppressed, or at least the German I had invited, by the founder. I became protective and intended to shelter the man I had invited. Completely unaware of the fact that a trauma was reconstructed by a collective narrative we were telling ourselves, which was only repeating past experiences.
We reconstruct situations that trigger our trauma in order to be able to heals this trauma, by becoming aware of the fact that the fight, flight or freeze survival response we developed back then, is not serving us anymore.