I remember running toward downtown Manhattan on Sept. 11, 2001, like it was yesterday.

I was in the National Guard then and studying at Hunter College when I saw the north tower of the World Trade Center get hit on TV. Without much thought, I ran down Lexington Avenue to my armory. I wasn't sure of anything except that I needed to be there. 

My fellow Guardsmen, many of whom were native New Yorkers like me, reacted the same way, showing up throughout the morning without being called in. 

I didn't watch what was happening in Pennsylvania or Washington, DC. I was experiencing what was happening to New York – watching police and firefighters headed toward danger, people fleeing as quickly as they could and, eventually, feeling the rumble of the towers collapsing. 

As I stood guard at Ground Zero for the next two weeks, I was processing collective trauma and rage I still cannot put into words. America was at war, and I believed almost anything we did next was righteous and justified. 

In the years that followed, I deployed to Afghanistan and Iraq and was fully on board with what we were doing. More hawk than dove, I championed the wars and believed that we could eliminate the terror threat and give these nations democracy, and that all would be well.

We just had to keep going.

But over time, the mission became harder to explain, even to ourselves. What began as a mission to punish those responsible for Sept. 11 and prevent........

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