It was only a snippet deep inside the newspaper, citing a few lines from a magazine article by the president's national security adviser, Richard V. Allen. But it struck me as of more enduring consequence, if true, then the controversy that now has Allen caught up in charges of receiving money for his part in a Japanese interview with Nancy Reagan.

In the article, Allen was said to have warned our European allies that the United States might well retreat into some sort of "Fortress America" isolation if the Europeans fail to accept the new American view of how to deal with the Soviet threat--in Europe and around the world.

The clear implication you got from the snippet was that this is Reagan administration policy. What you get from the full article is something altogether different: a tough-minded, coherent, comprehensive and articulate exposition of a perfectly respectable U.S. approach to the problems of the alliance --assuming, of course, that you are willing to accept some of the administration's more arguable premises.

But even if you don't agree (as I don't), you would have to rate Richard Allen on "The Atlantic Alliance at a Crossroad" in the fall issue of a publication called Strategic Review as, archaeologically speaking, a rare find.

The article's authenticity is reinforced, in part, by its not having been written in the overheated atmosphere of today's debate. Unlike the president's dramatic arms control offer, this was not a calculated effort to damp down the current cries from Europe of excessive American bellicosity.

It was not, in fact, originally written for publication at all. It is "based on a presentation" at a conference in Bad Godesberg, Germany, in September, the proceedings of which were not for attribution.

Its appearance in Strategic Review almost guaranteed its obscurity, this being a quarterly magazine to which you can't even subscribe unless you are an educational institution or a government agency. It is published mostly for the members of a think tank called the United States Strategic Institute.

All this emphasizes that Allen was playing to no large audience. Rather, he was quietly arguing the case for the new hard line in American policy in terms that took carefully into account the problems this creates for European allies.

He could "understand that Europeans are sensitive to abrupt changes in American policy," Allen wrote. He could see how some in Europe might think that the Americans, "having placed too much faith in d,etente in the first place, are now reacting with a characteristic anticommunist crusade--overdoing it once again."

He could see how the new swing in American policy might seem to threaten the "quite comfortable relationships" the Western Europeans had developed over the last two decades with their "Eastern neighbors" --and "enhance the danger of conflict."

What he wanted the Europeans to try to understand was that the United States had grievously neglected its defenses, even while the Europeans had been pretty good about maintaining theirs; that this undermined effective deterrence of war, which was the point of it all; and that this was something that ought rightly to be of common concern.

Where his argument may be less than convincing is partly in its heavy reliance, for an effective foreign defense policy, on the success of the American economic program. Partly it is in his seeming confidence that deployment of the American Pershing IIs and cruise missiles will proceed in the face of mounting European protest if the "double track" of negotiations with the Soviets over Theater Nuclear Force deployments should fail.

It was in this context that Allen addressed the "grim and bleak" alternatives if the United States and the Europeans cannot compromise their differences. "Should the Atlantic Alliance break apart," he wrote, "the United States might have to withdraw to its own hemisphere and Western Europe would be thrown onto its own resources."

But there was no threat expressed. And still less, he insisted in a telephone interview the other day, was one intended. "To talk about American withdrawal as an option is irresponsible," he insists. "It is not one we would actively seek."

In short, the pitch was positive. America's president, he said, "is pledged to restore the full deterrent power of the combined Western contributions to the common defense." But he went on to emphasize that the president recognizes the "difficulty of that task" and understands Europe's "cares and concerns."

A little more talk like that--and the president's speech this week is a constructive contribution--might be a useful antidote to recent and repeated public contemplation of nuclear shootouts confined to European battlefields.