"A lady's bedchamber in Bulgaria, in a small town near the Dragoman Pass. It is late in November in the year 1885." Using contextual clues and the mention of the year, the audience and readers can infer that the play is set during the height of the Serbo-Bulgarian War, which began in 1882.

The characters are also introduced in this act. We meet Raina Petkoff; her mother, Catherine Petkoff; and their maid, Louka. We also learn of Raina's lover, Sergius Saranoff, who has not yet returned from the battlefield. Later on in the act, we also meet Bluntschli, although he remains unnamed for now.

Finally, this act sets up the major conflict between romanticism and realism. We see the romanticism in Raina at her very introduction, as she sits "on the balcony . . . intensely conscious of the romantic beauty of the night, and of the fact that her own youth and beauty is a part of it." We also see it in smaller scale in her mother, who is described as rather pretentious—a woman "who might be a very specific specimen of the wife of a mountain farmer, but is determined to be a Viennese lady."

The realism is shown through Bluntschli, the Serbian soldier who enters Raina's room, in his matter-of-fact descriptions of life as a soldier and in his tearing down of Raina's fantasy of Sergius as a romanticised picture of chivalry and strength. We also see it in smaller scale in practical Louka, who appears to always be concerned with the here and now, in stark contrast to Raina.

George Bernard Shaw's play Arms and the Man is a play about both love and war. In a sense, Shaw sees these two themes as connected, in that romantic attitudes, which glamorize war and relationships rather than looking at them realistically, lead to bad outcomes in both the relationships among individuals and nations.

The first Act of Arms and the Man sets up the major conflict in the play between romantic ideals and reality, a conflict that plays out in the growth of the central character, Raina. At the opening of the play, Raina's mother is presented as enthralled with the glamour of war and of Sergius, the young hero to whom Raina is engaged. Raina is somewhat more ambivalent, but has no alternative models of either military or romantic ideals with which to compare her mother's views.

With the intrusion of Captain Bluntschli, not only does Shaw introduce a romantic alternative but also an ideological one. Thus the first act not only introduces the main characters and conflicts of the play, but also the ideas about war that Shaw wants to investigate through the vehicle of the play. Captain Bluntschli will serve almost as a mouthpiece for Shaw in the play.

Act I of Arms and the Man by George Bernard Shaw introduces two major themes of the play, the nature of love and war and the differences between their reality and the false images promulgated of them by romantic literature such as the works of Byron.

These themes are first introduced in the dialogue between Raina and her mother Catherine. Raina's fiancé Major Sergius Saranoff is an officer in the Bulgarian army and externally appears to be the perfect Byronic hero, leading a dramatic cavalry charge that overruns a machine gun post. In this initial conversation, Raina expresses some doubts as to her own romantic view of war and of Sergius, wondering if her ideas are only the product of opera and poetry, but then chastises herself for her doubts.

Captain Bluntschli, after he climbs onto the balcony, explains that the heroism of Sergius was actually an idiotic act that only succeeded due to the accident of the machine gun post having been supplied with the wrong ammunition. This introduces the main theme of the play, the difference between the reality of war and the portrait of war in heroic epics.

In Raina's developing relationship with Captain Bluntschli, we also see the difference between real love, in which Raina acts as an equal partner, saving Captain Bluntschli from the officers searching for fugitives, and the unrealistic infatuation with Sergius, based on superficial conventional beliefs rather than a real meeting of hearts and minds.

George Bernard Shaw was a self-effacing man, never concerned with how his comments and outspokenness would affect him. His main aim was always to share his message, and, in doing so, he would point out the shortcomings of any system of governance or unrealistic and over-romanticized views of life, love, and war, among others. In Arms and the Man, Shaw explores various ideas, and his views become apparent in his handling of the main issues.

In terms of theme, the central or main theme in any work is often universal in nature. It is particularly significant in Arms and the Man because Shaw's main theme of realism versus idealism is as relevant today as it was when the play was first performed in the 1890s. War, even if it appears necessary, is often over-idealized, divisive, and destructive, and yet there is still a romantic vision of a soldier returning from war as a hero, having removed a threat and saved a nation. However, even Sergius, the apparent hero of the day, recognizes the questionable nobility of war and its apparent contradiction when he says, “That is the whole secret of successful fighting. Get your enemy at a disadvantage; and never, on any account, fight him on equal terms.”

The paradox continues when Bluntschli, the man who would have been mercilessly killed had Raina not saved him, turns out to be a man whom Sergius and Paul hold in high esteem after the war; they even ask for his help. Shaw expertly reveals the predisposition of human nature, exposing its tendency toward frivolousness and inconsistency and not necessarily towards war, as some experts believe.

Upon hearing of his father’s death, Bluntschli makes plans to attend to his father’s affairs. His apparent matter-of-fact acceptance of his father’s death challenges the audience’s first impression of him. At first, when Bluntschli meets Raina, he is not a murderous, cruel enemy; he reveals a surprisingly soft side, with Raina even naming him her “chocolate-cream soldier.” Later, Raina makes a noteworthy observation, reinforcing the theme, when she says, “Grief!—a man who has been doing nothing but killing people for years! What does he care? What does any soldier care?” Shaw is defiant in his proposal that all is not what it seems. The concept of appearance versus reality fully supports the main theme of realism versus idealism.

George Bernard Shaw was himself a pacifist and Arms and the Man is one of several anti-war plays he wrote over his long career. The main literary device Shaw uses to evoke this theme and support his anti-war position is satire, ridiculing the ways people are misled into supporting wars.

The particular target of this satire is the Romantic artistic portrayal of war as magnificent and heroic. A secondary theme is equally romantic and unrealistic understandings of love. Shaw contrasts the ideals of love and war found in Romantic poetry and opera with their actual realities. The traditionally heroic Sergius is not only contrasted with the pragmatic Swiss mercenary but eventually shown to have his own doubts about the relationship of his image to his own inner feelings.

In the matter of love, the traditionally good match of the heroic soldier and the charming young lady luckily doesn't happen, for as Shaw shows us, it would have been a mismatch. Instead, true love develops as men reveal their weaknesses and search for true compatibility and women (Raina and Louka) are placed in roles where they can show strength and intelligence, characteristics far better as grounds for relationships than the Romantic ideal of the heroine who is constantly in need of rescue.