“like old beggars under sacks” – simile – dirty, dressed in rags
“coughing like hags” – simile – coughing as though they are sick
“Men marched asleep” – metaphor – exhausted
“blood-shod” – “shod” means to be wearing shoes – feet are covered with blood – sounds like “blood-shed”
“drunk with fatigue” – metaphor – suggests they are not walking straight – not fully in control – because they are so tired
“Gas! Gas!” – Exclamation marks show fear/ panic
“yelling”, “stumbling”, “floundering” – succession of verbs show failure to get the mask on
“drowning” – metaphor – can’t breathe – surrounded by green gas – looks like water