I think it will become a major topic to see TWL in relation to WWI since next year is the centennial of the War's start. Paul Fussell called the poem "a memory of War," though of course Eliot never went. Its impact on him, though, was very great. The letters have many places where he speaks of how hard it is and later how it was. And of course he was in Germany when it started and had to get his way out while surrounded by troop trains and German soldiers and general chaos. So in many ways, the poem is as much a poem of War--experienced from the Home Front--as post war. And chunks of it were written during the War. The post-war composition was not the same as a post-war poem. So Fussell's view is especially interesting now.
I think it was in Fussell that I first read the claim that "rat's alley" was a name for a trench, and the dead bodies were those of soldiers in and between trenches as much as any other place. David Jones described his own great War poem as being about "day by day in the Waste Land," and he did mean literally the devastated land of France as well as King Pellam's Land. The War does turn up in many places--Stetson, Albert who was just demobbed, the rats and dead bodies, and the passage from Hesse, for example.