Johnny Got His Gun is clearly an antiwar novel. While the root of this sentiment involves the brutality of war, Joe also protests the organization of modern warfare that has the interests of the moneyed classes as its purpose. Joe thinks in terms of an "us" vs. "them" axis, and it quickly becomes clear what he means by these vague designations. "Us," the archetypal little guy, refers to the poorer classes who work with their hands and make just enough money to be potentially happy within in their local life. "Them" refers to the upper, moneyed classes whose interests have dictated the war, yet who do not endanger themselves but instead send workers to fight against other workers. The oppression of the working classes by the upper classes is not a blunt matter of coercion. Instead, the novel tracks the ways in which power works through subtler means, such as through the misleading promise of abstract words such as "liberty." Socialism offers a helpful way of understanding the novel's politics, although nuances of Joe's convictions do not always strictly follow traditional socialist doctrines.
With Joe's conviction that war and its goals have nothing to do with him, or people like him, comes his understanding that people such as himself have nothing to gain by fighting in a war on terms of others. Joe understands that most men go to war for idealist hopes, but he is skeptical about the worth of these abstract ideals. Joe understands that abstract words like "democracy" and "freedom" can shift in meaning and are often meant to mean democracy or freedom for a specific few. Furthermore, Joe, with his unique position of being on the edge of life and death, can attest to the fact that dying men think only of their families, friends, and, most important, their wish to be alive—not about abstract ideals. Joe half-sarcastically suggests that men be offered concrete recompense for their fighting—a house, for example. Such compensation would perhaps alleviate the general feeling of being cheated that people such as Joe feel, making warfare seem slightly more "worth it." An important part of this theme, is Joe's tone of realism—he is there to say that the pain, injury, and deaths of war are not made nobler by an abstract cause; they are still horrific and to be avoided at all cost.
Near the beginning of Johnny Got His Gun, Joe feels the doctors amputate his arm. He wonders to himself where they will bury the arm and if they will honor it. The novel suggests that these are dilemmas that do not have to be addressed outside of modern warfare. Modern warfare creates unprecedented dilemmas and specimens of injury and decay. The unmatched horror of Joe's body is at the center of the novel, but this presence is reinforced by Joe's own remembered images and stories of men made grotesque by their war-torn bodies, such as the man whose face was burned off by a flare. The corollaries of the creation of these monstrosities by modern warfare are modern medicine and modern appetites. In Johnny Got His Gun, Trumbo portrays modern medicine as less a saving grace than an actual contributor to the monstrosities that war visits upon the body by war. Doctors manipulate damaged bodies for their own amusement and prestige, adding to the unnaturalness of soldier's bodies—as with the story of the doctors who sewed a flap over a man's open stomach wound so that others could lift it up and watch the man digest. The people with an interest in or an appetite for this sort of grotesqueness are the last by products of modern warfare. Joe understands the growing desire on the part of some people to see the freak casualties of war; he stresses his potential to serve as a visual attraction in order to get out of the hospital.
Related to Joe's horror at the monstrosities created by modern warfare and medicine is a subtle nostalgia for a pre-modern way of life. Joe's nostalgia for pastoralism also relates to his dissatisfaction with capitalism. Joe remembers fondly the ability of his mother and his father to produce, cook, and can all of their own food on the family's property and the vacant lot next door. Joe realizes that his father was a failure by the standards of modern capitalism, as he could never make enough money to save money. Nonetheless, Joe considers his father a success because his family always ate better than anyone, even the rich city people. Joe's nostalgia for the subsistence farming lifestyle also includes a desire for the time when the only concerns were local concerns, not national or international concerns such as warfare.