In a move likely to prove highly provocative to the Soviet Union, American and Japanese forces begin their largest postwar joint military exercises this Sunday.
The exercises, continuing until Oct. 5, will cover waters all around Japan, including sensitive areas close to Soviet territory. The nearby Soviet areas are bristling with military installations and nuclear and non-nuclear weaponry.
The military drill will encroach on waters where Soviet, American, and Japanese ships currently are jostling in a search for wreckage of the South Korean airliner shot down by the Soviets Sept. 1.
The timing of the exercise could not have been better chosen to aggravate Soviet anxieties and suspicions, even though it was planned long before the airline tragedy.
Some 150 Japanese ships and 117 aircraft will be involved in the exercises. The Japanese, in fact, are committing some 30,000 ground, air, and naval personnel, almost one-eighth of their entire military force. The Japan-based US Seventh Fleet is contributing 10 warships, 2 submarines, and an undisclosed number of aircraft.
From Oct. 1, the 81,600-ton nuclear-powered aircraft carrier Carl Vinson will be docked at Sasebo in southern Japan. Although Japanese military sources say it will not be ''directly involved,'' it will contribute to ''air control.''
Officially, the main theme of the exercise is to practice protection of Japan's strategic sea trade routes in time of war. But it also involves rushing troops from southern areas to the northern island of Hokkaido, which has always been regarded as the key Soviet invasion target in war.
The Soviets seized several small islands off Hokkaido from the Japanese at the end of World War II and have built army, air, and naval bases on several of them.
The Americans and Japanese will also practice blockading the narrow Tsugaru and Tsushima straits, two of the routes the Soviet Far East fleet would presumably use to reach the Pacific Ocean. The Soviet fleet consists of some 800 ships, including at least 80 major surface combatants, 30 ballistic-missile submarines, and at least 90 nuclear-attack submarines.
The US strategy is to ''bottle up'' the Soviets in the Sea of Japan before they can do much damage. But to many defense experts, it is also obvious that the exercise is a deliberate ''showing of the flag'' in an area which Moscow is trying to turn into a Soviet ''lake.''
But the longer range of new Soviet submarine missiles lessens the disadvantages of geography. Before, Soviet submarines had to slip into the Pacific Ocean to fire their missiles at US targets. Now, with a missile range estimated at some 5,000 miles, they can sit more securely in the Sea of Okhotsk and launch nuclear bombs into many Western US cities.
The military exercise has symbolic importance. Never has Japan thrown itself so wholeheartedly into military exercises with the US so close to Soviet territory.
Until only recently, the Tokyo government would have been reluctant to antagonize Moscow more than necessary, especially as relations between the two countries have not been good - with Tokyo's close defense ties with the US a major irritant.
The shooting down of the Korean airliner has helped to clarify Japanese minds more than any other event. Up to now, the ''growing Soviet military threat in the Far East,'' repeatedly referred to by Japan's Defense Agency in its annual report, has been seen by many Japanese as a mere justification by the military for a bigger defense budget.
Respected public opinion survey institutes conducted several studies in the days after the airliner incident to discover that 91.6 percent of the Japanese public regarded Soviet military force as a threat to Japan and 46.3 percent said Japan was not making adequate defense efforts.
There have never been such high figures like these before. Most polls previously have found the largest group of people believing Japan is spending enough on defense and does not have to do any more.
If this trend survives the dimming of public memories about the airline incident - and, with 29 Japanese dead, that might take some time - Prime Minister Yasuhiro Nakasone would seem to have a solid base for increasing Japanese defenses and also aligning Japan more closely with the US.
The shooting down of the jumbo jet has also demonstrated that the Soviets are not prepared to let anyone near their territory. That, of course, includes the Soviet-occupied islands of Japan's Northern Territories.
The Korean airliner tragedy has been a clear lesson in military realities for the Japanese public.
A number of defense analysts here believe the Korean airline incident is merely the start of a buildup of tensions in the Far East. And the Japanese seem to be slowly acknowledging that, like it or not, they are in the front line and had better be armed.
Public attitudes on this could well be clarified by a general election expected within the next few months. Judging by a recent Diet (parliamentary) debate, it will be a straight fight between the ruling Liberal Democratic party's pro-US, strong defense line and Masashi Ishibashi, the new leader of the main opposition Socialist Party who preaches unarmed neutrality.
For many, an article published by the leading newspaper the Asahi Shimbun last weekend proved a real eye-opener in demonstrating how much Japan is already committed to the pro-US, anti-Soviet strategy.
The Asahi claimed that there are 15 planes being operated from American bases in Japan providing a round-the-clock electronic and visual intelligence watch on Soviet Far East military activities. The planes include three high-flying SR-71 spy planes and 10 RC-135 electronic reconnaissance planes. (The Soviets allege that the Korean jumbo jet was mistaken for an RC-135.)
Added to this are two US nuclear submarines code-named ''Watchdog'' and ''Tomcat'' lurking on the floor of the Sea of Okhotsk to shadow their Soviet counterparts and monitor military communications, the Asahi claimed. (The Japanese do their spying from land-based listening posts in northern Hokkaido.)
In 1985 at least 48 F-16 fighters will be added to the base at Misawa, on the main island of Honshu but close to Hokkaido to improve the ''bottling up'' strategy in the north, and also reduce the present estimated three-to-one advantage the Soviets have in fighters in the region.
Anticipating this, the Soviets have been furiously building up their nuclear and non-nuclear capability throughout the Kurile Islands, on the Kamchatka peninsula, on Sakhalin, and on the Siberian mainland.
All this will likely be touched upon when US Defense Secretary Casper Weinberger passes through Tokyo this Saturday enroute for China.
In an interview published by the Tokyo daily Yomiuri Shimbun Sept. 21, Secretary Weinberger is quoted as saying: ''I don't know how much time we have in the Far East. . . . But I believe the sooner (the US and Japan) achieve a credible defense capability, the more likely we are to produce a more secure (defense) posture. . . .
''Confrontation in the Far East and northern Pacific is likely only if the Soviets feel they can effectively apply pressure against a weak, innocent, or disinterested party.''
His remarks were made in the context of a US feeling that Japan still has a long way to go to possess an effective conventional military deterrent.
Many more Japanese now appear to agree with him.