Hi Robert,
Thanks for the question on the difference between GCC High and DoD, the difference is that DoD is a DISA L5 environment restricted ONLY to DoD directly reporting to the US Department of Defense.
GCC High is L4 DISA and FedRamp High controls that has a controlled environment designed for Federal agencies, defense industry, aerospace industry, and other organizations holding Controlled Unclassified Information.
For more information on these definitions please refer to the service descriptions here:
https://technet.microsoft.com/en-us/library/mt774581.aspx
Nicole Berdy thanks for your comment, for clarification defense contractors that require FedRamp High, DFARs, and ITAR controls should be on the GCC High offering, which is what I believe you were referring to.
Thanks,
Dan