Existentialism in story "The Wall" by Jean Paul Sartre.

Existentialism is a cultural, literary, and philosophical movement that arose largely as a reaction to the unreflective optimism and belief in progress of the nineteenth century. It is not a set of fixed beliefs as so much an attitude toward life. Existentialism, in its various manifestations, emphasizes the lived experience of the subject, his or her existence, rather than positing any kind of underlying essence. For the existentialist, the world is one in which human beings are constantly confronted with their own freedom; they are forced to make decisions about how they will live their lives, which projects they will pursue, and how they will act towards others. Later on, we will see how these various elements come together in Sartre's "The Wall."
There has long been a tradition of religious existentialism; indeed, the first recognizably existentialist thinker of the modern period was Kierkegaard, whose passionately individualistic brand of Christianity established many of existentialism's key themes and concerns. For the most part, however, existentialism has tended to be associated with atheism. The work of Jean-Paul Sartre is a prime example.
For Sartre, the individual human being is all alone in the world, isolated from others by his radical subjectivity. This is a godless world, an absurd world without any intrinsic meaning or value. As subjects, we must create value, our own value, committing ourselves at every turn to decide who and what we shall be. Paradoxically, we are condemned to be free, and we are forced to choose our own fate, irrespective of the myriad external restrictions to which we are often subjected.
All of these themes are further developed in Sartre's short story "The Wall." The story concerns a group of soldiers serving with the International Brigade in Spain. One day they are captured by enemy forces and interrogated about the whereabouts of a local anarchist leader. None of the men divulge any information, and they are casually informed that they will be shot the next morning.
As the men await their terrible fate, the existentialist themes of the story come into play. Each man, confronted by the reality of his death, is forced to make a decision as to how he will conduct himself during his last few hours on earth. It takes their impending death to make the men realize that life, as Sartre would have it, can only truly be lived in the present. For it is only in the present that life in all its complexity can be lived and understood. It is in life that our inescapable freedom is exercised and our choices are made. Although the men are confined to a stinking prison cell, they are still existentially free according to Sartre; they can still choose how they will face their imminent demise; they can still live what is left of their lives without the illusions that have plagued their existence here on earth.
It is often said that we die alone, and this is an important existentialist theme in "The Wall." My death, like my life, is my own. Just as only I can live my life, only I can experience my death. It is my death that forces me to confront the utter absurdity and meaninglessness of existence. All three prisoners in "The Wall" have committed themselves to what they believe is a noble cause. Yet, in the figure of Pablo, all that has been swept away as he faces up to the cold, hard reality of his imminent execution. Just as he chose to confront the godless, meaningless world with commitment to a political cause, now he must choose again—this time abandoning his convictions to focus on the grim, sordid particulars of his death by firing squad.
Death disenchants, but it also clarifies. Pablo's commitment was his way of avoiding the inevitability of his death. However, in the end, whatever life projects we choose to pursue, the end is the same for all. We all die alone, dying our ownmost deaths. It is the same with Pablo's jailers; they will soon die too. Their inevitable fate, like Pablo's, is a microcosm of the human condition: we are all effectively under sentence of death. The difference lies in how we face up to that death and how we choose to confront our inescapable mortality. Pablo has made his choice; the jailers have made theirs. In the end, they all go into the dark, as do we all.