Launched in 2015, UK based Toby Groom (MA History and professional documentary maker for the History Channel) has created a fabulously succinct series of historical overviews. I'd suggest no one knows better how to build short documentaries than Toby and true to the title, Epic History TV is what you can reliably expect from this YouTube broadcaster.
This channel currently provides 43 episodes and all of them slick, multimedia products with professionally edited commentary ranging from 5 minutes through to just over an hour. What I particularly like is the use of animated graphics to illustrate unit movement from grand strategic down to tactical levels. Toby states his intention on his accompanying website to produce episodes monthly.
It's remarkable how much impactful content can be crammed into these historical overviews and they are a particularly helpful introduction to some of the wars and campaigns you may not be overly familiar with. Of special note is the growing Napoleonic series but subject matter ranges from the ancient periods to the 20th century.
Currently rating at 420,000+ subscribers this broadcaster fits squarely amongst the professional social broadcasters. He is supported through Patreon like all the full-timers and maintains an e-mail and twitter account for the channel. This is another of my firm favorites and something you can't get anywhere else.