The term “back to the wall” is an idiom that means a person or group of people are in a hard-pressed situation. It usually means the person or people have run out of options, or there are no means of escape. It also carries the connotation of a hard-pressed defense. The term developed out of the military and originally meant a last stand.
The notion stems from having no choice in a situation. “Back to the wall” insinuates there is an opponent against the protagonist or protagonists. This can be another fighter, another army or another sporting team. In such situations, the protagonist is under heavy pressure and has to fight hard just to survive as the only alternative is to give up.
Perhaps the most famous event to inspire such a term is the Battle of Thermopylae in 480 BC. In the battle, one of Sparta’s two kings, Leonidas, led 300 men in a fight against the Persian army. Joined by a small number of Thespians, they held off the advancing army for three days before finally being slaughtered.
In this battle, “back to the wall” is appropriate both figuratively and literally. The army made its stand in a tight valley between the mountains and the sea. If it had broke and ran, then the soldiers would have been slaughtered by the Persian cavalry anyway. The figurative wall was Greece herself. If they failed to protect Greece, then the Persians would have destroyed it.
Military encounters throughout history have thrown up occasions when one army was under great pressure from another and often had nowhere else to go. This is especially true of the allied, mostly British, army at Dunkirk in 1940. The same could be said for the defenders of castles and islands such as Iwo Jima in the Pacific War in 1945.
“Back to the wall” is often used in a sporting context. It refers to a vigorous defense by one team against the onslaught from another. For example, in football, one team may spend the majority of the game on the offensive. The other team had its backs against the wall, but somehow was victorious. A version of the idiom used in boxing, “on the ropes,” has similar connotations.