Delayed Teutonic migration
The Teutons were a Germanic tribe. Nick says that he went on a “delayed” trip to Germany because the United States joined the war late, and also because the war took a bit longer than expected. It could also refer to the teutonic order of knights, comparing WW1 to the crusades.
To help improve the meaning of these lyrics, visit “The Great Gatsby (Chapter I)” by F. Scott Fitzgerald and leave a comment on the lyrics box