Most of us learned to measure the distance that lightning was from our house by using the "Flash-to-Bang" method...when you saw the lightning you would begin to count "one Mississippi...two Mississippi...three Mississippi..." until the sound of the thunder arrived.  Then you divided the number of Mississippis by five and you got the number of miles away the lightning strike was.  When I joined the Army, I learned a new "Flash-to-Bang" formula:  it had to do with nuclear explosions.  The blast wave travels at about 13 miles per second, much faster than the speed of sound.  Soldiers in the field had to report the direction, time, and flash-to-bang information up their chain of command so the explosion could be accurately plotted.  The plotters had to figure in all the weather and winds and such to determine where the fallout cloud would go...referred to as "wind drift"...then they had to warn whoever was in the wind drift path to protect themselves.  If memory serves, this was called an NBC-1 report.  If enough soldiers reported in from enough different places, the explosion could be pretty accurately located.  Soldiers in the Cold War were particularly adept at this calculation because the greater the Flash-to-Bang number, the better your chances of surviving.  A half-second FtB was definitely not good.

Keep in mind that it has been a long time since I left the Army.  Things change.  But in my day we used the expression "Flash to Bang" to express the gap in time from a word to deed...or an order to a compliance...or...well, you get the idea. When referring to "No Flash-to-Bang", it meant that something happened almost immediately after a commitment to do it was made.

 
A lot of Army jargon is dark in nature...many of us realized that an NBC-1 might very well be the last communication we ever sent...blast waves were followed very closely by surface-of-the-sun temperatures, then after all that, a huge counter-blast comes back from the other  direction, filling in the vacuum caused by the initial blast wave.  None of these things are very good for the human body...but we practiced covering ourselves with our ponchos and putting on our protective masks knowing that we would most likely be found...if we were ever found at all...with all that stuff melted and fused to our naked skulls.  Somewhere in all of that, the release of tremendous amounts of radiation would clean out whoever was far enough out or deep enough down to avoid the effects of the other stuff.  The number of Japanese in and around Hiroshima that died in the blast was almost doubled by the number who died in the following weeks as their insides melted and turned to mush...radiation poisoning.  Every Cold Warrior knew that if the Russians crossed the border and tried to make a run across Northern Germany, the only way we could stop them was the use of "tactical nukes"...small nuclear weapons...low-yield artillery shells and rockets.  And the Russians would immediately respond in kind.  The folks who patrolled the border referred to themselves as "speed bumps" but in truth, once the poopoo got to the propellor, we were all destined to be crispy critters in a matter of hours.  
Well...that deteriorated into a gruesome little tale.  It started earlier today when MamaCharlie said she liked the phrase "Flash to Bang" and the way we used to use it and said she would like to see an article with that title.  Soooo...here it is.  Just another meandering through the brain of an old Army lifer with nothing better to do than try to please his lady.  But not too bad a "Flash-to-Bang" on this one, huh?