Because drag changes when spoken of in the past i.e. he was dragged or they drug him down the long road, the pale rock and brown. Down dust, a knocking path. And to drag has a begin point (though two are considered): begins when man is bound; begins also with one first tug.
So we take the word to our own uses and say:
it begins with his head on the ground with his hair loose
under shoulders and shirt with snaps, they’re mother-of-pearl. Then begins a yank
and slide, begins his skin and scalp—
begins a break a tear, red to pink
to precious white; then begins what is
his skull, glisten of star
to bone.