None of the aging, ailing communist leaders has been the subject of more Kremlin watching and waiting in recent years than has President Josip Broz Tito of Yugoslavia. The Soviet hierarchy obviously has been hoping to use Tito's demise to restore its hold on his strategic Balkan stronghold.

But the old partisan fighter -- a thorn in the Russian bear's paw for virtually the entire three-and-a-half decades of his rule -- may have succeeded in dashing the Kremlin's high hopes one last time. Several secret U.S. intelligence reports describe the apparatus set up by Tito in the past 10 or 12 years to prevent Soviet domination of Yugoslavia after his death. If his plans work out -- and U.S. analysts think there's a good chance they will -- the maverick communist leader will give his antique adversaries in Moscow a posthumous poke in the eye.

The heart of Tito's grand plan is the assurance that an Afghanistan-style adventure by the Kemlin would exact a fearful toll. This assurance, in Tito's view, would be enough to dissuade the Soviets from embarking on such an adventure.

One secret report, prepared by the Defense Intelligence Agency, analyzes Tito's overall strategy this way: "Tito has continued a two-faceted policy toward the U.S.S.R. . . . which reflects a sensitivity to Soviet interests in Yugoslavia without yielding Yugoslav independence. Tito appeared, for example, to want to balance dependence on foreigh weapons sources between the United States and the U.S.S.R. At the same time, Yugoslav military exercises . . . clearly advertise resolve and capabilities to defend the homeland."

A top-secret CIA report notes that the Yugoslavs at one point took their concerns directly to the U.S. ambassador in Belgrade. "Senior military officers told the U.S. ambassador that Yugoslavia is interested in closer military relations," the report states. "One officer played down the regime's occasional assertions that the West posed a threat to Yugoslavia as merely a political maneuver."

As for the effect of Tito's stategy on the Kremlin, the DIA analysis says: "Such careful orchestation of Yugoslav-Soviet relations [by Tito] probably reduces the likelihood of overt Soviet meddling in Yugoslavia, but not Soviet desires to increase its influence there."

Here's how the defense intelligence experts assess the chances of Soviet domination after Tito's death:

"Without Tito's guiding hand, the Soviets might expect a larger measure of success . . . but we estimate that:

" -- The Yugoslav Federation will survive in spite of internal problems that will seriously threaten it.

" -- The U.S.S.R. is unlikely to invade a cohesive Yugoslavia, and the Yugoslav military will serve as an effective and possibly the priamry unifying force."

In recent year, Tito worked feverishly to strenghten his nation's military capability. His success in this crucial venture was measured in a U.S. intelligence document whose title says it all: "Yugoslavia's Strategy Is to Make Any Invader Pay a Heavy Price."

Yugoslavia has a standing army and air force of 250,000, bolstered by more than a million trained reservists known as "territiorials." U.S. intelligence analysts had this to say about the role of the reserves:

"Yugloslavia's defense system places great emphasis on the territorial force, a nationwide partisan force . . . organized and trained at the local level. The territorial force, an outgrowth of Yugoslav concerns over the Soviet invasion of Czechoslovakia in 1968, is made up of both men and women . . . .

"The national defense law of 1968, strengthened in 1974, makes every citizen responsible for resisting foreign attack . . . . The government and military take every opportunity to demonstrate that an attack on the country would involve a potential aggressor in a protracted, bloody conflict."

The Kremlin watched closely as the partisan network took shape. And while the Soviets publicly pooh-poohed the creation of guerrilla forces, one intelligence report notes, "Belgrade has strongly criticized Moscow for belittling these partisan accomplishments."

The citizen soldiers would be Yugoslavia's second line of defense. A secret U.S. report explains that, as Tito planned it, the country's defense "would rest initially on the regular army, which would engage the enemy along the borders and delay the advance until the territorials could be mobilized."

The big flaw in the partisan system, my associate bob Sherman was told, is that the Yugloslav territorials are poorly armed, and only a small percentage of them have seen military service in recent years. "They're equipped primarily with small arms, mostly old weapons cast of by regular units," a source noted.

Still, U.S. analysts feel, the Yugoslavs are equipped, by terrain, tradition and temperament, to wage the kind of guerrilla warfare that could seriously disrupt the Red Army -- just as Yugoslav (and Russian) partisans harassed the Nazi war machine during World War II.

The key to Titio's hoped-for legacy of continued independence is an orderly succession to power after his death, and eternal vigilance against Soviet infiltration. A new constitution set up a complex system of collective leadership, and the Communist Party apparatus was revamped for tighter disipline. And in 1974, a DIA report noted, Tito purged his top military leadership of pro-Soviet elements. Tito's power as head of state will pass to two deputies after his death. They have been making decisions at the aging partisan's bedside since a renewed illness threatened his life.