Japan debates Soviet military buildup. Discussion centers on how serious Soviet threat is

Hiroyuki Maruyama laughingly describes himself as a man with a ``desperate'' cause. He is defying the leaders of his own Japan Socialist Party, the nation's leading opposition party which advocates ``unarmed neutrality,'' by warning publicly of a growing Soviet military threat to Japan.

Mr. Maruyama's concerns reflect a growing public debate here about how much of a threat the rapid Soviet military buildup in East Asia really poses to Japan.

In recent years, the Soviets have greatly expanded their Pacific Fleet with both ships and nuclear missile-bearing submarines; have put troops on the Kurile Islands just off the coast of Japan; have put medium-range nuclear missiles in East Asia; and have expanded and updated their Air Force in the region. This buildup is certain to be one focus of United States Defense Secretary Caspar Weinberger's two-day visit here through Saturday.

Unlike in the US or Western Europe, debating military issues is relatively new here. It was just seven years ago that the Japanese defense minister caused a minor political uproar when he officially characterized the Soviet Union, for the first time, as a ``potential threat'' to Japan.

Now, says Col. Shigeki Nishimura, of the Japanese Army's defense planning staff, ``we have moved from [discussing] whether or not the Self-Defense Forces should exist to what they should do.''

The freshness of the debate is understandably surprising to many in the West, where the NATO and Warsaw Pact armies have been facing off across a heavily fortified frontier for 40 years. But in this island nation, there is a sense of distance from the East-West conflict. ``Emotionally our people want to be neutral,'' explains Maruyama. He attributes this feeling to the antiwar legacy of World War II.

The late 1970s saw the beginnings of a change in Japanese perceptions. The Soviet invasion of Afghanistan had some impact, but the primary reason, analysts here agree, is that the Soviet buildup on the ``Pacific front'' became evident at this time.

``Since 1978,'' says Colonel Nishimura,``there has been a clear pattern that Soviet forces began to be directed at the Pacific front as well as the Sino-Soviet border.''

Most striking has been the expansion of the Soviet Pacific Fleet, now the largest of four. Since the mid-1970s, according to official Japanese figures, the fleet has increased by about a third. It now numbers about 835 ships, including 90 major surface vessels and 140 submarines (half of them nuclear-powered). In 1979, one of the Soviet Navy's two aircraft carriers joined the Pacific Fleet, followed two years ago by a second carrier.

The most attention-getting event for the Japanese public was the appearance in 1978, for the first time in 18 years, of Soviet ground troops only miles off Japan's shores. The troops, plus aircraft, were stationed on the disputed ``Northern Territories,'' four small islands of the Kurile chain claimed by Japan and occupied by the Soviet Union after World War II.

The late '70s were also marked by the appearance of Soviet SS-20 intermediate-range nuclear missiles in East Asia. These weapons, 170 by the official US count, can reach China and Japan. And the nuclear-powered ballistic missile-carrying submarine fleet also underwent rapid growth -- from 11 subs in 1974 to 24 in 1979.

The bare facts of the Soviet buildup are now well known, but there are great differences over how to interpret them. Critics of Japan's current arms increases like Kiyofuku Chuma, defense specialist for the Asahi Shimbun, one of Japan's leading newspapers, argue that ``in this area, the Soviet intention is not offensive but defensive.'' They say the military balance in the Pacific remains strongly in the US's favor, an assessment shared by many US defense analysts.

The Soviet Union, these critics say, has no particular cause to threaten Japan. Unlike in Central Europe or on the Sino-Soviet border, there is no historical basis in the postwar period for a Soviet-Japanese conflict. The only danger to Japan, their argument goes, comes from Japan's overinvolvement in the US's global confrontation with the Soviet Union.

This view is shaped by the peculiarity of Japan's postwar defense policy. The current interpretation of Japan's US-imposed antiwar Constitution restricts its military to a purely defensive role.

The proponents of Japanese rearmament agree that there is no serious threat of an isolated Soviet attack on Japan, but they emphasize the word ``isolated.'' Japan is a target, they say, because of its geographic position relative to the Soviet Far East.

The Soviet Pacific submarine fleet constitutes a third of the Soviets' most modern Delta-class subs. They carry new long-range missiles that can reach North America from the Sea of Okhotsk, which lies off the Soviet mainland just north of Japan. Okhotsk has become, like the Barents Sea in the Arctic, an ``ocean bastion,'' as US military sources put it, to be defended against US attack in time of crisis.

Japan, Nishimura notes, sits astride the three narrow straits that provide an exit for the Vladivostok-based Soviet Pacific Fleet out of the Sea of Japan. Under circumstances of global confrontation, Japan would be a priority target, the rearmament proponents say.

The Soviet Union, their argument goes, would act to assert ``sea control'' over these areas as part of its ``inner zone'' of defense. Nishimura and Maruyama both suggest that, in such a situation, it is consistent with Soviet doctrine that Moscow would try to seize northern Hokkaido in order to control the Soya Strait and would try to threaten lines of communication between the US and Japan.

Both Nishimura and Maruyama have broken new ground by presenting this kind of discussion to the general public.

``It is necessary,'' says Maruyama, ``to make a real estimate of Soviet intentions if we want Japan to remain independent, particularly from Soviet military pressure.''