Outside, it was a bright October night, the kind of night they ought to reserve for high school football: full moon hanging low and fat in the sky, crisp air bringing the blood to attention, the kind of night where you could almost hear the low chant of the partisan crowd cheering on the home team when the ball is in the other team's hands: Dee-fense, dee-fense, dee-fense.

Inside the American Institute of Architects building, where the Committee for National Security was throwing itself a first anniversary party, there was no question as to whose hands the ball was in: The talk was defense all right, and the mood was bleak.

Then again, maybe bleak is too strong a word for the mood that prevailed among the group of about 50 who gathered at the reception. Former U.N. ambassador Andrew Young, for instance, was sounding cautiously optimistic. Sort of. "My feeling is that there is an alternative that has not evolved a consensus yet and that that's what this committee has been trying to do," he said, as a trail of admirers came to shake his hand and wish him well.

No, said associate director Jane Wales, bleak about summed it up after a day that many committee members spent finding out just how bad things really looked for those who incline to the more-guns-doesn't-mean-better-national-security point of view. She quoted one committee member who prefaced a question to pollster Peter Hart during the committee meeting with the threat, "If you don't answer this question with encouraging news, I'm going to jump out the window."

The committee was started last year in an effort to stimulate public debate on national security issues and to wean the public away from seeing such issues as purely military matters. And it describes itself as bipartisan, although most of its 60 members tend to lean to the liberal Democratic side of the fence. At the party, the enormous birthday cake and the trays of cold meats went virtually ignored, and the white-wine sipping was on the light to sparse side. The talk, however, was intense: There was much discussion of AWACS, B1s, and ABMs, not to mention MX missiles, superhardened silos and the ever popular window of vulnerability.

Sen. Charles Percy (R-Ill.), the guest speaker, was by far the most optimistic voice, telling the assembled that the administration's record on arms control could be seen like the proverbial glass of water, as half empty or half full, and that he inclined toward the latter perspective. "Much has been accomplished in the last nine months," Percy said. "To those who are anxious about what has yet to be achieved or demonstrated, I would point out that things might well have been far worse."

"In a field where the possible ways in which things could get worse don't dead end until they reach nuclear holocaust," one guest remarked rather amiably, "you could say he's got a point."