What is Jonass first startling and disturbing memory?

Jonas's first startling and disturbing memory occurs when he experiences the concept of war during a training session as a Receiver of Memory. He is overwhelmed by the chaos, fear, and pain associated with battle, which starkly contrasts with the controlled and safe environment of his community. This memory reveals the darker aspects of human experience that have been suppressed in his society, highlighting the depth of sacrifice that comes with the pursuit of sameness and security.