The things they carried.

I am now beginning my second book the things they carried. As I read into it, I am realizing that the setup of this book is extremely different than that of The Sun Also Rises. The first chapter begins with the author describing the soldiers and he especially likes to describe the items that they carried and the weight. I'm not really sure what what purpose this has. However, its purpose could be to truly show the reader the burdens of the men in Vietnam. Also, I was curious when I came across the part when the author described humping. He described it was walking or marching and also to hump something was to carry it. Is that really how the word is used or is it used as humor?