In the novel, Knowles uses Finny's altered attitude to the war as a symbol of loss and regret. In the beginning of the novel, Finny uses his "pink shirt" as an "Emblem" to commemorate the bombing of central Europe.

Knowles utilises the theme of war to highlight how the boys daily lives are effected by it. During the summer session, the teachers and maids leave Devon due to the war; leaving the boys with their responsibilities. This is seen to effect the boys since Finny frustratingly questions about all the "crap about no maids". The language he uses clearly expresses his irritation with the situation because for so long he has depended on the maids to make his bed, but now he is left to do it himself. This emphasises the hardship that the war brings to the boys lives and makes the audience sympathises with them because the war entered so abruptly and made all these changes, and now they are left to fend for themselves. Therefore, Knowles intentionally utilises Finny's frustration to highlight how the war is constantly looming over the boys lives. Furthermore, with the teachers leaving also came with more lenient rules and regulations for the boys. This is seen when Mr. Ludsbury glosses over the boys breaking rules and saying "it didn't matter". After the war started to become more relevant within Devon, the teachers were not as strict because the boys reminded them of youth and innocence (as it was their last year before having to enlist). Knowles incorporates the theme of youth to contrast the theme of war and highlight the fact that the war is creeping into the boys lives and will later demolish the youth they have left. Also, this is emphasised through the title of the novel, 'a separate peace'. The word 'separate' means unconnected and divided and 'peace' means calmness and serenity. Knowles uses the title to show how the boys are divided from the war as long as they are in a tranquil place, which is Devon. Hence, WW2 functions in the novel through the ways it effects the boys daily lives but also how they are still separate from the war since their youth is still within them as long as they are in Devon.

Knowles uses the war as a symbol of boy's behaviour and actions. Knowles states that "because (Gene's) war ended before (he) ever put on (his) uniform: (he) was on active duty all (his) time at school; (he) killed his enemy there". Symbolically, the war reflects the inner conflict Gene has. It was Gene's fear that causes him to rival Phineas, a sort of private war of physical and mental ability. The ongoing war represents, not just Gene's private war, but all the other characters as well. The war also symbolises the boys' views on their own personal battles. For instance, Phineas states that "there isn't any war". This reflects Phineas' view on his own private war. As Phineas thinks that everyone around him idolises Phineas, he thinks that he has no personal enemies or battles. This is why the war, to him, is fake.

In the novel, Knowles uses Finny's altered attitude to the war as a symbol of loss and regret. In the beginning of the novel, Finny uses his "pink shirt" as an "Emblem" to commemorate the bombing of central Europe. This means that Finny wishes to congratulate and celebrate the success of the USA in the war. This suggests that Finny liked the idea of war, perhaps because it was linked to sports as there still are two teams competing against each other because they have similar interests. There is a misconception here because Finny makes his point of thinking that "everybody wins" at sport very clear, and that there is no losing team, evolving from his constant habit to win at sports. The misconception is that there is no winner in war, and that everyone loses, soldiers, money, men etc. The pink shirt further introduces the idea of contrast, as the colour pink has connotations of femininity and tenderness, where as war is a harsh and dangerous event. 

An emblem is a symbolic object that is used as a distinctive badge of a nation. Using the pink shirt, Finny is defined as a patriot by Knowles, and the readers can infer that Finny is patriotic enough to risk his life and join the war. This viewpoint then quickly changes, towards the middle of the book, when Finny gets injured, and then believes that the war is staged by "some fat, old men." The words 'fat' and 'old' suggest that these 'men' didn't, and don't, pay attention to their health and fitness, which in Finny's eyes is an immediate disgrace to human kind. The idea that the war is staged suggests that Finny trys to make himself feel better about not being able to go to the war and fighting for his country, by not believing in the war at all. This branches out from his injury, from which the reader can infer that Finny regrets climbing that tree, because he lost so much that day. This makes the reader feel sorrow the inconsolable Finny. The idea of loss and regret ties in well with the war as there is only loss when a war going on and not 'everyone wins' [in fact, no one wins]