Given it is the 100th anniversary of the start of the Great War a lot of people will write on this subject.
What I have always found interesting is that the leaders of the allied forces learnt nothing from the US Civil war, the Boer war or the Franco-German war. They instead looked to 'wars' that had occurred in their colonies.
A lot of Generals both had a history with the Calvary and still had an affinity for it.
Remarkably It was our own John Monash who came up with original tactics to use. He was never really liked after all He was an engineer not a professional soldier , He was Australian and worst of all he was a Jew ( with a mistress in London!).
At the end of the war The treaty of Versailles ensured a bitter German population given no battles were ever had on Germany.
One interesting development was how the war ensured the major social issues of the day in all nations was papered over.
Here is a nice piece by John Quiggin.
Best book to read on this topic is undoubtedly Dreadnought