There is a juxtaposition here between the octave, which is set in the present tense, and the volta, which is set in the future tense. Owen uses the octave to juxtapose a scene of war. The octave is the first 14 lines, and it also had an A-B rhyme scheme. The poem then transitions to the volta for 4 lines, and switches to a D-C rhyme scheme. Then, the last two lines rhyme with each other separately from the octave and the volta. So, just physically on the page, grammatically, and formally– the first half juxtaposes the second half. It juxtaposes it in tense, subject matter, and location as well. The first half is set in battle while the second returns home.