The animal symbolism in the story is quite prominent. The four pigeons are the most likely to survive because of their ability to fly above the fray created by mankind. It is thought that pigeons mate for life, suggesting that they possess a loyalty that humans often lack and intensifying the indictment against mankind's propensity for violence and destruction.
The goats seem likely to perish. It may be that Hemingway is alluding to scapegoats, which are traditionally seen as sacrificial animals for man's sins. These poor animals may become collateral damage in a war in which they have no stake.
A marked characteristic of cats is that they are independent, adaptable survivors with "nine lives." Because of these strengths, the man and the narrator are likely correct that the cat will survive because of its ability to elude mankind when it becomes necessary.
The age of the old man has imparted wisdom; he describes himself as apolitical, a wise choice in this time and place, when and where the government is unstable. Taking a side could be deadly and therefore not worth the risk. Life arguably becomes more precious to people as they approach their final years, and squandering it in a futile battle is a choice the old man would not make. The fact that he wears glasses implies that he is able to metaphorically see life clearly.
The bridge could metaphorically represent the divide between war and peace, safety and danger, and life and death. The narrator's final thoughts are ambiguous, echoed by the gray, obscuring clouds and suggesting that there could be death, but perhaps tempered by a resurrection.