So, this is a poem about war, right? Yes sir. War stuff is just plain all over the place in these lines. Trenches, flags, death, violence, soldiers—it's all crammed into this one little poem. And none of it is good. Even things that usually give us a feeling of pride, like, say, flags and drums, are associated with senseless violence.
Line 2: War is death, and the woman's lover has died in battle. Or is he just throwing his hands up in frustration? Nah, that doesn't sound right. We're betting this is actually this is a nice, roundabout way of saying he died without actually saying he died.
Line 3: Believe it or not, horses used to be a big part of warfare (now it's Humvees, tanks, and planes). The rider-less horse here symbolizes the death of the lover.
Line 6: The drums are "hoarse," which means they've been used a lot and are probably starting to lose their voices, so to speak. The drums "boom," which makes them sound like bombs or missiles. This is a strange contrast—they're hoarse, but they also boom?
Line 7: These souls are the soldiers who, apparently, are "thirsty" for some battle. Souls is here an example of synecdoche, a figure in which a part (soul) stands in for the whole (the soldiers themselves).
Line 8: Soldiers being drilled, soldiers being killed—seems like a pretty accurate description of war and the military to us. This makes the soldiers look like cattle being led to the slaughter; to this guy, war makes animals of men.
Line 9: The "glory" refers to a flag, that age-old symbol of pride, one's country, patriotism, you name it. Note the contrast here. The flag is high up in the air, but the soldiers are down below, in the trenches, dying for it.
Line 11: Fields are great, but not when there's a war going on. A nice, pretty field becomes a giant graveyard, full of a thousand corpses. Wait, you mean this field isn't a kingdom (10)? Well, it is, but the gravest (did we just make a pun?) kingdom you'll ever see.
Line 13: Babies losing fathers in yellow trenches? Yep, that happens in war too, all the time actually. The color yellow here symbolizes death, disease, or anything gross and unhealthy. The tumbling refers to part of the process of dying; the speaker means that he's been stabbed, or shot, or otherwise incapacitated. He tumbles because he's lost control of his body.
Line 14: We can imagine that many soldiers, if they aren't immediately killed, probably grab their bodies and take one last gulp before they die. Note the perverse way in which the "thirst" of the soldiers becomes the "gulping" of the dying soldier. Nice, Mr. Crane, nice.
Line 17: Here's that pesky glory again, only here it's actually called a "blazing flag." Blazing here doesn't mean it's on fire, but that it's flying in the air. The word "blazing" makes us think of fire, though, and thus of the fires of war. And note again the way the flag flies high in the sky, while the soldiers are being killed and drilled down below, far away from that thing they fight for.
Line 18: The flag has an eagle with a crest of red and gold, and the colors here are significant. Red makes us think of blood and thus of war. The gold reminds us of those yellow trenches and thus of death, sickness, dying and the like instead of, say, nice jewelry or King Tut. The flag might as well be a giant symbol of warfare and its causes.
Line 19: The guy talking here is like a mean sergeant, with no respect for soldiers, human life, or any of the other things war can destroy.
Lines 20-21: If the sergeant guy is talking, this is definitely a cruel, cruel man. But there's also some savage irony going on here. There's nothing virtuous about slaughter, and nothing excellent about killing.
Line 22: Ah, and here is our old friend the field with a thousand corpses again. Oh how we wish it were the other kind of field—you know, the one filled with frolicking fawns and such?