Does D5 mean DEFCON 5? Where are we as far as DEFCON? DEFCON 4 is a state of heightened alertness. DEFCON 4 is the first level of readiness above the baseline value of DEFCON 5 and thus constitutes a fairly mild, but significant, and more widespread increase in readiness level. This DEFCON level signifies increases intelligence-gathering efforts and, sometimes, the heightening of national security measures. However, it is not usually an indication that the military (or the nation) are in imminent danger of attack. In the modern world, it is thought that DEFCON 4 is sometimes issued after minor to moderate terrorist attacks and politically-motivated killings, or after would-be plots are uncovered. Presumably, this is done in anticipation of further violence as an attempt to prepare for and prevent it. DEFCON 5 is a state of peacetime military awareness. A DEFCON level of 5 is a very good thing, this is the condition used to designate normal peacetime military readiness. At a DEFCON 5, the US military takes no wide-scale precautionary defence measures beyond what is ordinarily required.  Note that DEFCON 5 isn't necessarily a sign that the world is at peace — conflicts, even major ones, may be occurring around the world during a DEFCON 5. However, in this state of awareness, the military judges that these events pose no significant defence threats. My belief is that IF (big if) Q is talking about DEFCON when he said D5, we were in DEFCON 4 state of military awareness, and after accomplishing the mission, we are reverting back a D5 level, a state of less intelligence gathering and less precautionary defence awareness measures.