As I am but an humble American citizen and cannot legally access the latest season of Downton Abbey, what I can say about the happenings and history of series two will derive from what spoilers I glean from articles and stray tweets. So Edwardian Promenade and I are forced to march out of step with my fellow British Downtonites until it airs on PBS in January. However, never fear, I have many Edwardian & WWI tricks to pull my from hat!
For now, I direct you to Trench Warfare: A Manual for Officers and Men (1917) by J. S. Smith.
Click on the page to open the book: