The head-hunting tribes of the island of Borneo have finally been subdued. It is a unique irony of this century that their indirect conquerors are the Japanese, whose heads they last hunted a little over four decades ago.

Young Iban tribesmen, weaned on heroic tales of yesteryear, now go off to work on offshore rigs, drilling oil that goes mostly to Japan. They buy Japanese cars, televisions and stereos, even as the skulls of the invading Japanese of World War II hang in their tribal villages.

The story of the Ibans unfolded as Dale Van Atta recently traveled back in time, up the jungled Belait River of tiny Brunei to the Iban villages of today.

The Ibans are a brown-skinned people of medium build who were relative latecomers to the Moslem sultanate of Brunei. It became apparent that the Ibans began a grisly practice of collecting heads based on their belief that the immortal spirit of the enemy resided in the head. The ritual became a rite of passage. Each young Iban male was required to acquire an enemy skull to prove his manhood.

It degenerated over the centuries to even uglier deaths. Instead of taking heads in battle, Iban men soon considered any pate fair game. Children who strayed too far from their villages ran a great risk, as did elderly women.

The practice slowly faded during a century-long reign of Britain's "white rajahs" beginning in 1841. The first, James Brooke, was a British adventurer who ended Iban piracy and then ruled the area with wisdom and brute force. When necessary, Brooke didn't hesitate to unleash the head-hunting Ibans to enforce his rule. But he and his descendants managed to substitute cock fighting as a primary means of settling disputes.

But when the Japanese successfully invaded in December 1941, the British once again encouraged the Ibans to become head hunters. Hundreds of Japanese, possibly thousands, fell to Iban parangs, sharp jungle knives. Several dozen small skulls Van Atta viewed in a rabbit-hutch-like enclosure far up the Belait River were all Japanese, according to his river guide, Benny Foo. Foo explained that the holes at the top of each skull were made by the Ibans.

Naturally, all this made the Ibans the most feared guerrillas the Japanese faced in the region, so the invaders stayed along the coast, leaving the interior to the Ibans. When the Japanese finally fled the island before American forces, they set fire to Brunei's 38 oil wells. The blaze took four months to extinguish, and it was not many years before Brunei was selling the same crude oil to postwar Japan.

Today, half of Brunei's crude oil is sold to Tokyo, while the Japanese have the exclusive contract for Brunei's natural gas. The oil riches have made Brunei's subjects, including the Ibans, quite comfortable.

Though the older Ibans continue to farm and hunt, the young men prefer working for the national oil company, or for the government, which is primarily funded through Japanese contracts. Few of them seem to grasp the historical irony that the modern-day Tokyo has had such a direct hand in civilizing and subduing a once-fierce tribe, which Imperial Japan had so feared.