ABC World News Tonight (Channel 7 at 7) begins an unusual 10-part report on America's military might and preparedness.

It is not a subject that lends, itself to the usual network news attempts at comforting even-handedness: hawk or dove, you'll find something in "Second to None?" to scare the daylights out of you.

In the first five segments, diplomatic correspondent Ted Koppel traces the erosion of some of the precepts of the "mutual assured destruction" (MAD, of course) doctrine which has underlaid our military planning over the past 15 years or so.

Basically, that always discomfiting theory holds that neither the United States nor the Soviet Union would dare launch a preemptive (first) nuclear missile strike because the other side's counterstrike would be equally destructive.

But now, Koppel points out in a series of depressing vignettes, the security of U.S. land-based missiles from attack is in doubt, the Soviet Union is spending $2 billion a year on a concerted civil defense program and current U.S. plans for achieving at least parity in those and other areas are either lagging or nonexistent.

In the most chilling segment, to be seen tomorrow night, the basic assumption of any "mutual terror" standoff takes a terrible thumping.

North American Air Defense (NORAD) stages a "war game" detailing the steps the huge U.S. defense machine would have to take in order to retaliate, should an enemy launch a preemptive strike.

Except for the occasional radio "test" for CD, it's been a long time since we've had to recall any aspect of that terrifying Cold War timetable: just 24 minutes after an enemy launch in which to notify the civilian population, assemble and disperse U.S. leaders and gather sufficient data to make the "right" decision for a counterstrike.

Koppel doesn't bother to point it out, but given the chances of an enemy-jammed communications satellite and a sleepy White House helicopter pilot or two and the whole 24-minute scenario seems dreadfully absurd.

With a SALT treaty debate just around the corner, the assumptions this series tackles should raise some political hackles around town. No matter what strategic or political alternative the viewer may privately hold out for, there's some grim news for everbody in this timely ABC series.