Continuing on this series of videos supporting the WW2 Channel, this is part one of a two-part look at how the US Army ended up with the armored force with which it entered combat in North Africa.
Forging the Thunderbolt (Gillie)
Men on Iron Ponies (Morton)
Greasy Automatons and the Horsey Set (Tedesco)
A number of Center of Military History documents
A few other things I've forgotten about, but the above will get you 90% of the way there.
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Christie Tank Video
1930 Cavalry Journal.
1939 Cavalry Journal
Soviet doctrine video.
Interview with Ken Estes on USMC tank history
Assessment of USMC light tanks.
About The Chieftain
The Chieftain (Real name Nicholas Moran) is Wargaming America's resident tanker and amateur historian.