It really isn't anti-war - or perhaps I should say that, in the context and setting the story takes place, it ought not to be termed anti-war. More accurately the movie is anti-glorification of war. I found that, on reflection, there's a feeling of "something not quite right" about the movie, even though I thoroughly enjoyed it.
The setting is England during World War II and just before D-Day. To have been anti-war at that juncture would have meant being willing to allow Hitler and his Nazis to overrun Britain as they had already overrun much of Europe. Sometimes war, horrific as it is, becomes inevitable. I'll not natter on further about the general storyline of the movie, but instead use TCM's brief synopsis. A few viewer reviews, positive and negative, can be found at the link too.
In wartime London just before D-Day, Lieut. Comdr. Charlie Madison, an aide to eccentric Rear Admiral Jessup, specializes in supplying the top Navy officers with luxuries such as party girls. Madison is an exponent of cowardice as a virtue because he believes reverence of heroism promotes war. He falls in love with Emily Barham, his British motorpool driver, a young woman who has lost her husband and brother in the war. Admiral Jessup is obsessed with the idea that the Army has a better image than the Navy and is determined that the first dead man on Omaha Beach on D-Day be a sailor. Jessup orders Madison to photograph the D-Day landing, and, despite his protests which alienate Emily, Madison is forced at gunpoint to be the first man to land on Omaha Beach. Running from the bombs, Madison trips a land mine and is reported to be the first man killed in the invasion. Photographs of his supposedly dead body appear in the newspapers, and he becomes a hero, but later he is found alive. Admiral Jessup then organizes a hero's welcome for Madison, but he threatens to confess the true story of his cowardice to the press. Emily, in a reversal of sentiment, promises to marry him if he will keep his secret, and Madison agrees to remain quiet.
The Am of Em was an adaptation of William Bradford Huie's novel, which, according to a comparison at Wikipedia carries no comparable message to that of the movie. The reason isn't hard to find. It was Paddy Chayefsky who developed novel to screenplay - the same Paddy Chayefsky who penned that well-remembered "mad as Hell" speech from the movie Network. For more about him see two archived posts HERE and HERE. I'll simply mention here that he was born 29 January 1923 - Sun in Aquarius!
Chayefski said, it is reported, that he treated the serious-toned novel as satire. His screenplay's theme of cowardice as a virtue, and the wrong-headed glorification and absurdities of war and its heroes, has no parallel in the novel.
The novel briefly mentions that Emily's mother, Mrs.Barham, has been mentally scarred by loss of her husband and son, but she is not a major character. The movie has a long and memorable scene between Charlie Madison (James Garner) and Mrs. Barham (the wonderful Joyce Grenfell), full of eloquent (some say preachy) antiwar rhetoric, in which Charlie breaks down Mrs. Barham's denial of the loss of her husband and son, and reduces her to tears while nevertheless insisting that he has performed an act of kindness. The novel has no parallel to this scene, but it's the key scene of the film. Here it is:
It has to be kept in mind that the movie was released in 1964, in the midst of the USA's war in Vietnam. The sentiments expressed have to be taken in with that in mind, otherwise there'd be a danger of disrespect for those, military and civilian, who died in World War II in opposition to the very real and imminently encroaching scourge of Naziism. The movie shouldn't be seen or described as "anti-war", but as anti-glorification of war, anti- the naming of streets after heroes, anti- the building of statues to Generals and, anti- making war so heroic and noble that young people will feel it their duty to be eager to go to war. I'll add my own anti- here: anti the ubiquitous (in the USA) bumper stickers, declarations on TV at every opportunity, along the lines of: "God bless our troops" "We support our heroic military", "Thank you for your service". In other words, nowadays viewers would be wise to take the message offered by the movie, but be sure to put it into a context relevant to our own times - which is what Chayefski did in 1964.
My husband quickly recognised the film's background music, a piece especially important to him. One of his jazz idols, Paul Desmond, recorded a melody titled Emily, which husband has always loved, but had been unaware it had connection to this movie.
Emily, composed by Johnny Mandel, lyrics by Johnny Mercer. A version with lyrics, sung by Sinatra, below, and jazzy rendition by Stan Getz and Bill Evans (my own favourite version), and a link to Paul Desmond's version too.