back to the wall

[back to the wall] or [back against the wall] {adv. phr.} In a trap, with no way to escape; in bad trouble.

The soldiers had their backs to the wall.

He was in debt and could not get any help; his back was against the wall.

The team had their backs to the wall in the second half.

Compare: BETWEEN THE DEVIL AND THE DEEP BLUE SEA, LAST DITCH, ON THE SPOT, UP AGAINST IT.