Returning, We Hear the Larks
by Isaac Rosenberg
   
Sombre the night is.  
And though we have our lives, we know  
What sinister threat lurks there.  
   
Dragging these anguished limbs, we only know  
This poison-blasted track opens on our camp — 5
On a little safe sleep.  
   
But hark! joy — joy — strange joy.  
Lo! heights of night ringing with unseen larks.  
Music showering our upturned list’ning faces.  
   
Death could drop from the dark 10
As easily as song —  
But song only dropped,  
Like a blind man’s dreams on the sand  
By dangerous tides,  
Like a girl’s dark hair for she dreams no ruin lies there, 15
Or her kisses where a serpent hides.  
   
 

poison-blasted —The Germans had introduced poison gas on the western front in 1915. The first gas used was chlorine. If you have ever worked with bleach, you have some idea of how much of an irritant it can be, and of course breathing it in gaseous form is much worse than dealing with fumes from the liquid form. Upon significant inhalation, it almost immediately destroyed the victim’s sinuses, esophegas, and lungs. However, it was visibly green and much heavier than air, so soldiers soon learned how to save themselves in a gas attack. It also caused immediate violent choking, which ironically could prevent the soldier from inhaling it deeply. The next gas used was phosgene. It was not quite as deadly, but it was also not immediately as irritating. Soldiers would breathe phosgene gas and still be able to function, then collpase and sometimes die 24-48 hours later. Chlorine and phosgene gas were routinely combined into a cocktail called white star. The Germans introduced mustard gas (known also as Yperite) in 1917. Colorless and virtually odorless, it caused blisters on the skin, in the lungs, and on the eyes, often rendering the victim blind. Its effects did not manifest as quickly as those of chlorine gas but were felt much sooner than those of phosgene, generally within a few hours. Also, unlike the earlier gases, which were relased from open canisters and required the prevailing winds to be blowing in the right direction (and which also explains why the Germans used them with much more devastating effects on the Russian front, where the prevailing winds were in their favor), mustard gas was loaded into artillery shells. Rosenberg is almost certainly referring here to mustard gas, because unlike other gases, which dissipated quickly, mustard gas settled into the ground and could remain dangerous for a month or more, depending on the weather.

The French and British used poison gas as well; the French even experimented with a type of nerve gas. But the British attempted to keep their use secret for purposes of propaganda.
 
larks — Larks, as you know by now, were common birds on the western front. But Rosenberg is also aware that McCrae had used the larks as a symbol of bravery in “In Flanders Fields.”