From: Iowan in MD/DC
I've been listening to this series for the past month or so, and am just about finished. I have perhaps a half-hour left of the last episode. This is not a quick series - the average episode length is just short of 4 hours (23h 4m in total); it's called "Hardcore History" for a reason. All 6 episodes are free to download - the Blueprint for Armageddon series.
I highly recommend for anyone interested in learning all the ins and outs of the first world war. It mostly focuses on the Western Front, but bounces around to Russia, Turkey, and other places at times as significant events occur in those places. I always had a general idea of WW1 (that it was a lot of stalemate, really horrific trench warfare and no-man's land with poisonous shell holes-turned-drowning pools, Verdun, mustard gas, etc.), but after listening to this I feel like I have a much greater appreciation for what happened year to year and why things happened... and how horrific a lot of it was, even above and beyond a lot of WW2 stuff that I've learned about.
The guy is also great at incorporating quotes from primary sources, and his narration style is easy to listen to. After listening to these 24 hours of free content, I am thinking I may purchase a few of his other episodes.
For WW2 Eastern Front folks, or those interested in learning, he does have a 4-part series on it (Ghosts of the Ostfront) that was rated the 5th-best podcast ever (according to Slate magazine).