SSDI is probably the hardest to get awarded, but for good reason. The rules explicitly state that you cannot apply if you are still working and that to be given SSDI, you must be unable to work in any capacity (labor, office, etc.). That's a pretty high standard. Having DoD 100%/VA 100% rating does not guarantee SSDI. You must prove that you are unable to work in any capacity.
There is a loophole for "Wounded Warriors" where the SSA recognizes that you may be unable to work and also held on active duty for some period of time. In a normal private sector civilian job, you would be let go, or retained without pay for some period of time. Because of this, SSA allows you to apply for SSDI while still on active duty, however, you must claim "Wounded Warrior" status and prove you are unable to work. If your application implies that you are working in any capacity while still on active duty, they will probably deny it.
Bottom line with SSDI whether you're on active duty or not: You must prove your conditions prevent you from working in any gainful capacity.