When a disabled Soviet nuclear submarine sailed bithely into Japan's territorial waters last week in defiance of stern warnings from Tokyo, the Japanese were forced to draw some unpleasant conclusions.
"There is an old Russian proverb that states, 'Cry like a wolf when living with the wolves,' "observed one official here.
"The [submarine] incident has taught us the lesson that Japan cannot disregard 'power'."
It also neatly underlined the message of the recently published annual Japanese defense white paper that the Soviet military buildup in the Far East has reached the stage where it is "intended for something considerably more than mere defense."
And it demonstrated just how difficult it is for Japan to remain a nonnuclear island in the midst of a big-power nuclear sea.
Japan's most immediate concern was the possibility of radioactive contamination after the Echo-1 class submarine allegedly caught fire off the southern island of Okinawa on Aug. 21, killing nine crewmen, apparently by asphyxiation.
But after several days of shadowing the disabled vessel as it was towed toward its Siberian home base of Vladivostock, and after taking regular water samples, experts said no leak from its nuclear reactor had been detected.
But the increasing number of accidents involving Soviet nuclear submarines remains a serious concern here.
Japanese and American experts noted that the submarines are fitted with pressurized water reactors, the type made notorious by the film "The China Syndrome" and the Three Mile Island accident. In theory at least, there is a risk of reactor "meltdown" releasing an intensely radioactive core into the sea. The risk increases with older vessels like the Echo-1 class.
Citing its experience as the only country to have been atom-bombed, Japan has maintained three principles: not to manufacture, possess, or permit on its soil or in its territorial waters, any form of nuclear weapon.
US nuclear submarines have to obtain special permission to enter their regular base ports in Japan. Despite a bilateral security treaty, the United States is forbidden to store nuclear weapons at its Japannese bases.)
Thus, the Tokyo government refused the Soviet submarine permission to pass through Japanese territorial waters because of the danger of radioactive contamination, as well as lack of a guarantee that it carried no nuclear weapons.
The Russians went ahead regardless, forcing the Japanese to backpedal and accept the fait accompli by labeling the intrusion as "innocent passage" guaranteed under international maritime law.
Even so, Soviet disregard of Japanese sensitivities has left new scars on the troubled Moscow-Tokyo relationship, as well as making the Japanese "principles" look rather empty.
No one was surprised to find a Soviet vessel off Okinawa, however. The Soviet Far East fleet is believed to have 130 submarines, about half of them nuclear.
The Echo-1 class was a "first generation" type rushed out in the early 1960s and quickly superseded. The five submarines of this type in service were converted from nuclear-missile carriers to torpedo carriers. The Japanese Naval Institute says they are utilized in small "anti-carrier" groups with surface vessels, operating primarily in the Indian and Pacific Oceans.
These groups recently have been monitoring US naval movements between the Seventh Fleet base at Yokosuka, near Tokyo, Subic Bay in the Philippines, and the Pacific fleet headquarters at Pearl Harbor.
Operating off Okinawa, they are close to what remains a strategic American base (the island, then under US control, played a major logistics role during the Vietnam war) as well as straddling Japan's vital trade routes.
Against this large Soviet force, the Japanese have 13 conventional submarines. Their antisubmarine capability currently consists of 132 patrol planes, 59 helicopters, and 47 destroyers.
Defense planners are working on a strengthening of this capability over the next three years.
Nevertheless, Tokyo officials observe that the Soviet Union's total disregard of warnings concerning the disabled submarine's intrusion into Japanese territorial waters demonstrates what Moscow thinks of Japan's current military capacity.
It has given the government considerable cause for further thought.