In the Second World War the common experience of soldiers was dire long-term exile at an unbridgeable distance from "home." One fought as far from home as Alsace is from California, or Guadalcanal from Manhattan, or Bengasi from Birmingham and Berlin. "Shipping out" is significantly a phrase belonging to the Second War, not the First. And once committed to the war, one stayed away until it should be over.
By contrast, what makes experience in the Great War unique and gives it a special freight of irony is the ridiculous proximity of the trenches to home. Just seventy miles from "this stinking world of sticky trickling earth" was the rich plush of London theater seats and the perfume, alcohol, and cigar smoke of the Cafe Royal. The avenue to these things was familiar and easy: on their two-week leaves from the front, the officers rode the same Channel boats they had known in peacetime, and the presence of the same porters and stewards ("Nice to serve you again. Sir") provided a ghastly pretence of normality. One officer on leave, observed by Arnold Bennett late in 1917, "had breakfasted in the trenches and dined in his club in London."
The absurdity of it all became an obsession. One soldier spoke for everyone when he wrote home, "England is so absurdly near." Another, bogged down in the Salient in September, 1917, devoted many passages of his diary to considering the anomaly: "I often think how strange it is that quiet home life is going on at Weybridge, and everywhere else in England, all the time that these terrific things are happening here." Remembering the war fifty years afterwards and shaping his recollections into a novel, one participant discovers that the thing he finds especially "hard to believe" about the war is this farcical proximity. On the way back up the line on a train, one officer returning from leave remarks to others in his compartment: "Christ! ... I was at Chu Chin Chow last night with my wife. Hard to believe, isn't it?" And the narrator observes:
Hard to believe. Impossible to believe. That other life, so near in time and distance, was something led by different men. Two lives that bore no relation to each other. That was what they all felt, the bloody lot of them.
~ From The Great War and Modern Memory by Paul Fussell, p. 64