I can't really keep my eye on the archer because it seems she will be engulfed by the pushing shields at any moment.
The arrangement of the shields and soldiers just doesn't seem to allow anything moving in the diagonal direction the atcher does.
But I think that's the strength. Because of the crowding shields and soldiers and the archer breaking the arrangement in a unnatural fashion the feeling of hasty oppurtunity and despair is emphasized.
It's like a visual, silent, desperate warcry.
But I don't know anything about compositions. This is just how I feel the picture works for me.
Life is like a box of chocolates, when you're a fat glutton it lasts shorter.