I was privileged not long ago to join a gathering of several former Army chiefs of staff. These were the leaders of the Army I grew up in, from the 1970s until my retirement from active service in 2013.
They were, and are still, to me, legendary figures who seem larger than life. Most are Vietnam veterans who led our Army through a period of massive transformation. All served during America’s most recent period of great-power competition—the Cold War. They understood and led change in the Army.
But one of them said something that, at first, I didn’t understand: “We find ourselves in an era that...