John McCrae's poem "In Flanders Fields" is one of the most famous poems of the First World War, and its predominant theme is the nobility of sacrifice. Written after the Second Battle of Ypres in early 1915, it quickly became popularized in pro-war propaganda literature in both the United Kingdom and McCrae's own native Canada. The imagery of poppies came to symbolize the lives lost in war—a symbolism still in place today in the United Kingdom and many Commonwealth countries, where red poppies are worn for Remembrance Day (November 11th), commemorating the end of the First World War, and wreaths of red poppies are placed on war memorials throughout the country in honor of the fallen.
McCrae's poem has been co-opted in the service of patriotic feeling, and a whole tradition of remembrance has sprung up based on his words:
Take up our quarrel with the foe:
To you from failing hands we throw
The torch; be yours to hold it high.
If ye break faith with us who die
We shall not sleep, though poppies grow
In Flanders fields.
The speakers are exhorting their fellow soldiers to continue fighting, to "keep the faith" for which the dead sacrificed their lives. This exhortation is very much in the vein of other early First World War poetry, in that it seems to present the war as a just cause. To die in the service of that cause is tragic, but noble. The imagery of flowers, sunsets, and birdsong is juxtaposed with the sounds of heavy artillery to present death as a kind of beautiful haven from the chaos of war. The dead are honorable, their deaths are poignant, and it falls to you, the reader, to ensure that their deaths are also meaningful by continuing the struggle against "the foe."
There is no suggestion here of the ugly realities of the war—realities with which McCrae, a field medic, was painfully familiar. Instead, the reader views the situation from the perspective of the "larks, still bravely singing," far above the noise and horror, removed from the immediate facts to a place where theoretical "torches" can be passed from the dead to the living, and the entire brutal exercise can still be held to have meaning and purpose.