Every military infantry division needs a name.

Most get numbers, and some have nicknames. The 42nd Infantry Division got a rainbow.

The story of how is one of the most interesting origin stories in American military history.

The diagnosis did not exist, but the damage did.

Post-traumatic stress disorder was not in the diagnostic vocabulary in 1945. It would not be formally recognized by the American Psychiatric Association until 1980, thirty-five years after the end of the Second World War, following the sustained advocacy of Vietnam veterans and the mental health professionals who treated them.

But the condition existed. It has always existed.