I began my service to country in a war, a bitter war that frayed and nearly shredded the fabric of America. I finished my last tour of service to country in a mission of peace. In the final month of my service as secretary of state, I was back in Vietnam one more time, on the Mekong Delta where the rivers I’d patrolled in combat had become rivers the United States was now protecting from environmental degradation.

Back on the Bay Hap River, where almost forty-eight years before I’d come face-to-face with my own mortality, staring down the business end of a Viet Cong B-40 rocket launcher, I met a man whose mission that day in 1969 was to kill me and my crew. ...

I looked at him and thought, How crazy is this? Years ago, when we were young, we were both heeding the call of our leaders, trying to kill each other. But now we stood there in peace, a peace I had been privileged in some small way to help make real by first making peace at home. If that doesn’t make you an optimist, nothing will.