"Many had lost their boots But limped on, blood-shod. All went lame; all blind;" (5-6)
The trench warfare of WWI caused lots of soldiers' legs to rot. Literally. Mired in mud and gore, the soldiers often had to spend hours (if not days) standing in trenches. The detailed description of how men come to be wounded is followed by sweeping statements about the condition of all soldiers.
"If in some smothering dreams you too could pace Behind the wagon that we flung him in," (17-18)
Owen's phrasing here is intentionally vague: does the experience seem like a "smothering dream" to those who are living it, or would the reader have to enter into a dream-state in order to understand it?