How was the return from war different for Vietnam veterans than for those of earlier wars? please answer from the passage thank you

Although most veterans were not permanently damaged by the war, some 15 to 25 percent of Vietnam veterans (between 500,000 and 700,000) suffered from a stress-related impairment known as post-traumatic stress disorder (PTSD), a psychological disease brought on by acute combat experience.

She was one of the world's first female heads of state.