The really quick, really accessible version is the Extra Credits videos, though understand that they simplified a lot of things, and made some mistakes (which they admit to in a follow-up video).
The Great War YouTube channel also covers some of the same ground in an accessible but more rigorous manner, though I don't remember them going over all the "clash of empires" background stuff.
On the far other end, I liked the book The War That Ended Peace by Margaret MacMillan. It's a dense tome, but it's chock full of details.
I'm just getting to the end of reading Orconomics, and it had a somewhat novel take on this. Basically, elves live so long that their entire personality can change century over century because they meet, and subsequently outlive, so many new people.