The XB-70 Valkyrie predated the Concorde by well over a decade - and would have been a far more capable military platform than the Concorde ever would (Mach 3, a large internal bomb load, and range).
It was cancelled because it had become apparent that 'high and fast' simply wasn't enough against the emerging air defenses - and that was in the 1960's.
So my first question would be - "What could a military Concorde bring to the table that the XB-70 wouldn't have done better?"