fall out

As they trooped toward the minibus, he saw three of the phoners fall out of line. Two of them began biting and fighting and tearing at each other’s clothes, snarling what could have been words –Clay thought he heard the phrase bitch-cake, but he supposed it might just have been a coincidental occurrence of syllables. The third simply turned and began walking away, hiking down the white line toward Newfield.
‘That’s right, fall out, sojer!’ Denise yelled hysterically.
Source: Cell by Stephen King

What does the verbal phrase fall out mean?

Thank you.

When soldiers are in formation and they are told to "Fall out!" they leave the formation and go their separate ways. The "sojer" is intended to be "soldier."