As I read more about the first world war, it's becoming clear to me that most of what I learned in school was incomplete at best, wrong at worst. I've just started reading "The Myth of the Great War", and it's amazing how the military narrative was affected by the ultimate victors. I remember reading about the great victory of the allies at the Marne (September, 1914). It's pretty clear that nothing of the sort happened. The German offensives had reached the end of their supply lines, and had not reduced the protective forts around Verdun - so they withdrew to a defensible set of lines. The BEF had been more or less destroyed, and the French had lost about a third of their army - and a week after the pullback, the Germans were pushing successful offensives again.
There's a lot more to read - but after the statistics of the Ferguson book, it's clear to me that the Entente powers were lucky not to lose in 1914, and would have lost in 1918 had the US not entered the war. The Entente powers spent most of the war on the wrong side of the force exchange, consistently losing more men than the Germans, and consistently losing battles.
Of course, the biggest conclusion to draw from all of this is what Ferguson drew at the end of "The Pity of War" - the war was a huge error, probably the biggest one of the last few hundred years (and I include WWII in that list - without WWI, I doubt there would have been a WWII). That was made painfully clear in the book "Europe's Last Summer", where the mistakes that flowed from the assassination of the Archduke Franz Ferdinand led to the war. It's a fascinating subject, but also a deeply disturbing one.