Push them back.
( ( ( Push them ) back ) . )
(ROOT (S (VP (VBP Push) (NP (PRP them)) (ADVP (RB back))) (. .)))
They must be shoved back and left there.
( They ( ( must ( be ( ( ( shoved back ) and ) ( left there ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (MD must) (VP (VB be) (VP (VP (VBN shoved) (ADVP (RB back))) (CC and) (VP (VBN left) (ADVP (RB there)))))) (. .)))