Wars have an adverse effect on our lives. How does the story "Old Man at the Bridge" bring out this truth?

The titular old man is "without politics," as he says in response to the narrator's question. Throughout the narrator's conversation with the old man, we learn several other things about him: he is seventy-six years old, a native of San Carlos, and a caretaker of animals, which he had to leave behind "because of the artillery." He has no family, but he worries tremendously about the animals. He says:

The cat, of course, will be all right. A cat can look out for itself, but I cannot think what will become of the others.

The old man is a peaceful man: he wears spectacles and dusty clothes, does not take sides in political arguing, and constantly returns to his refrain: "I was taking care of animals . . . I was only taking care of animals." Indeed, he is an innocent civilian: a man who has been forced to leave behind the only things left in the world that he cares about because of the impending violence.
The narrator actively choses to participate in the war:

It was my business to cross the bridge, explore the bridgehead beyond and find out to what point the enemy had advanced.

However, the old man does not. He simply wants to live the rest of his life quietly with the animals as his companions. Instead, he will now likely die alone in a strange place because of a war he takes no side in and wants no part of. Thus, Hemingway elucidates the idea that war has an adverse effect on our lives because, even if we prefer pacifism, war will inevitably intrude on the peace we have constructed.