These soldiers seem to give a reason to fight in every stanza. In the first stanza, the soldiers make a point of how there is this beautiful scene saying how it starts with In Flanders Field(1) with poppies blow[ing](1) and larks, still bravely singing(4) being ignored and disrupted by the guns(5). It is as if they are saying that we should fight to stop the fighting for the sake of nature and peace.
The second stanza gives the thoughts to people who have lost something to the war. This is when the reader is exposed up front and right in their face that this is from the Dead(6). That these people once lived(7) and loved(8). People similar to the reader and now are dead. The third stanza sets out for the reader to take up [the Deads] quarrel with the foe(10). This stanza tries to implore the reader to take up the cause and fight for the cause. It seems as though the author put the reason to fight of each stanza in the first line of each stanza.