Before Japan's new prime minister, Yasuhiro Nakasone, came to breakfast with Washington Post editors and reporters on Jan. 18, his embassy went over every detail of the arrangements, even insisting on knowing where each of the 23 participants would sit.

They programmed everything but Nakasone, whose surprisingly strong remarks about Japan's military posture went far beyond previously stated positions. When the remarks were published in early editions of the next day's Post, they touched off an explosive reaction among the Japanese reporters who had accompanied Nakasone from Tokyo but who did not attend the breakfast.

That was only the beginning of the repercussions. Nakasone's remarks brought a stern warning from Moscow and inquiries from Peking, and are still the subject of heated debate inside Japan.

Because I was the one who questioned Nakasone on defense at the breakfast, I have been especially fascinated by the reactions. After the tumult began, I felt as if I had somehow tripped a lever in a Rube Goldberg machine, causing a pea to drop on an arm and chain of moving parts to start a monumental landslide.

This became all the more curious when I learned days later that the most oft-quoted phrase in Nakasone's statement actually was not uttered at the breakfast by the prime minister but was the colorful interpolation of his official translator, dealing extemporaneously with Nakasone's staccato language on a complex subject.

Nakasone was quoted as saying that Japan should become "an unsinkable aircraft carrier" (in Japanese, fuchin kubo) to defend against penetration by the Soviet Backfire bomber. What he actually said, according to a close inspection of the tape recording of the breakfast, is that Japan should be "a big aircraft carrier" (okina koku bokan) to block the Russian planes.

To an American ear, the difference between an "unsinkable" carrier and a "big" carrier is not so great, but for Japanese the difference is much greater. The editor of the Japan Times, Kiyoaki Murata, wrote that for older Japanese fuchin kubo is reminiscent of the patriotic phrases applied to "unsinkable" aircraft carriers and battleships of the Imperial Japanese Navy in World War II -- before the craft in question actually were sunk under U.S. assault.

The other image which the "unsinkable" phrase evokes in the Japanese mind, wrote Murata, is of "Japan as a formidable fortress, loaded with high-performance fighters and bombers and bristling with powerful missiles." He said this is almost as odious an image to the mostly pacifistic Japanese as a socialist state is to most Americans.

The resonating phrase aside, it's clear that the substance of Nakasone's remarks represented a major change in the stated policy of the Japanese government. In response to my question about his military views, Nakasone replied in rapid succession that:

"There should be no taboo" about revising the 1946 constitution, in which Japan formally renounced war and pledged never to maintain military forces. (A tortured reinterpretation of the latter point has permitted Japan to build and maintain "defense forces" but the whole subject is highly controversial in Japan.)

Japan's air defense should aim to stop the Soviet Backfire bomber from penetrating Japanese airspace, a capability which would require a large scale military buildup to accomplish. (Nakasone repeated the same point to President Reagan several hours after the Post breakfast, according to U.S. officials.)

Japan should aim for "complete and full control" of strategic straits controlling the Sea of Japan "so that there should be no passage of Soviet submarines and other naval activities" in time of emergency. (Such action by Japan to bottle up the Soviet fleet long has been at the top of the U.S. military's wish list, but considered too politically sensitive to be mentioned in public.)

Any one of these statements by a Japanese prime minister would be enough in most circumstances to generate a roaring controversy in Tokyo. The three together added up to announcement of a far reaching change in Japanese policies and attitudes, amounting to a basic shift in Japan's military role in the world. The resulting storm has sharply reduced Nakasone's popularity at home, especially among women voters, changing the prospects of his administration.

The trip to Washington was Nakasone's first transPacific voyage as prime minister. I wondered later whether he had any understanding or even premonition as he answered between bites of breakfast that his statements would rise from the eggs and bacon to the pages of The Washington Post, to the eyes of the watchful Japanese press, to breakfast tables throughout Japan and the following day, to the echo chambers of Japanese politics and on to Moscow and Peking.

It was completely clear that these remarks were "on the record," since the ground rules had been established at the start of the meeting and a tape recorder placed right in front of Nakasone. But did he come to Washington prepared to make these statements whenever asked, and simply did so at the first chance (the Post breakfast being the intial event of his three-day visit)? Or did he spontaneously say in Washington what he would not say in Tokyo, somehow failing to realize how far and fast his words would fly?

Nakasone long has held the views that he expressed, but an aide said that so far as is known, the prime minister had not made a specific decision in advance to publicize them in Washington. There were hints in some of his remarks that he saw the breakfast as disconnected from Japanese politics, as when he said, "the constitution is a very delicate issue and I have in my mind a very long- range timetable, sooto speak, but I would not dare mention it even in our Diet."

After the contoversy over the breakfast erupted, Nakasone handled the press questions cautiously in a press conference translated into English primarily for American reporters. But in a similar session immediately afterward for the Japanese press, beamed to Japanese homes via television satellite, he denied that he told the Post what had been attributed to him. A few hours later, on his plane en route home, he said he had been confused by the questions and denied the earlier denial.

It is unclear whether Nakasone realized at the time that, in fact, he had not said in Japanese the most vividly quotable thing that had been attributed to him in English. By the time he left Washington the "unsinkable aircraft carrier" had steamed far out of port, with Japan's policies and Nakasone's fortunes taking a heavy pounding in stormy seas.