Emperor Hirohito, who presided over Japan's entry into the disaster of World War II and its subsequent emergence as a great economic power, died Saturday morning at the age of 87.

Hirohito occupied the Chrysanthemum Throne for 63 years, longer than any of his ancestors in a bloodline of 124 rulers reaching back more than 2,600 years. He was the world's longest reigning monarch and the last of the world war's dominant figures, having outlived by decades Roosevelt, Churchill, Stalin and Hitler.The emperor is succeeded by his son, Crown Prince Akihito, 55, who had been acting as regent in his ailing father's place. Akihito's accession was marked by a brief ceremony in which he took possession of the three treasures of the Japanese throne - a sword, a jewel and a mirror. The formal enthronement of the new monarch in a sacred Shinto rite is to take place only after the official mourning period for Hirohito is completed, between one and two years from now.

In addition to Akihito, the emperor is survived by his wife, Empress Nagako, 85, who is in fragile health; another son; three daughters; and 10 grandchildren.

Hirohito's health deteriorated after he underwent surgery for cancer of the pancreas a year ago. His condition worsened suddenly on Sept. 19, and since then he had been receiving intensive medical care in his bedroom at Fukiage Palace, in central Tokyo.

The people of Japan watched with an increasing sense of horror and pity as daily newscasts reiterated a litany of Hirohito's blood pressure, temperature, pulse and respiration in much the same tone as the stock market fluctuations. Throughout the four-month struggle, court physicians administered more than six gallons of blood to the hemorrhaging emperor. They never acknowledged that he was suffering from cancer.

When he ascended to Japan's Chrysanthemum Throne on Christmas Day 1926, Emperor Hirohito named his reign Showa, which means Enlightened Peace. Fifteen years later, on Dec. 7, 1941, he went to war against the United States.

With his death, in keeping with ancient tradition, he will henceforth be known as Emperor Showa. But whether Hirohito was indeed a man of enlightened peace - or a man of war - is a question historians still have not resolved.

Certainly the stooped, frail octogenarian was all but impossibly cast as a warmonger during World War II, given his fondness for plant and animal life. Even as a young monarch, Hirohito seemed more at home hovering over a microscope, peer-ing at a rare species of sea creature, than astride a stallion.

But doubts about his role in the Pacific conflict persist.

The emperor didn't prevent his generals from starting it, even though he was convinced that Ja-pan could not defeat the United States and its economic might. He approved the surprise attack on Pearl Harbor, even applying the imperial seal to the declaration of war that came three hours after Japanese bombs began falling on "Battleship Row."

Nor did he intervene to stop the atrocities perpetrated by Japanese troops on countless Americans, Europeans and Asians.

Many years later, in an interview with Japanese news organizations, Hirohito said that he had agreed to the war because his Cabinet ministers had voted for one and he felt obliged to abide by the government's decision.

What is significant to many Japanese is not that Hirohito approved the start of World War II but that he agreed to stop it, in defiance of his generals and ministers, who wanted to fight on even after atomic bombs were dropped on Hiroshima and Nagasaki.

"While there are, of course, some Japanese who hold the emperor responsible for the war," said Ikuhito Hata, a historian, "most consider him a brave man for bringing it to an end. Most of us believe he saved our lives."

On the morning of Aug. 14, 1945, several days after the atomic bombs fell, the emperor summoned Cabinet members and military commanders to his emergency underground quarters beneath the bomb-gutted Imperial Palace. Dressed in an olive-drab army uniform and wearing white gloves, his face gray with despair, Hirohito listened while the others failed to agree on whether they should accede to the Allies' demands for unconditional surrender.

Finally, in his odd, high-pitched voice, the emperor spoke.

"I want you all to agree with my conclusions . . . that we cannot continue the war any longer . . . " His voice broke and the emperor wiped a tear beneath his glasses. "I realize full well how difficult it will be for the loyal officers and men of the army and navy to surrender their arms to the enemy and see their country occupied, and perhaps stand accused of being war criminals. . . . But I cannot let my subjects suffer any longer."

Hirohito's wishes were immediately obeyed. At noon the next day, millions of Japanese crowded around radios to hear a sound they had never heard, the "Voice of the Crane" - their emperor. He ordered unconditional surrender, although his rationalization for declaring war was recognized by many as disingenous.

"We declared war on America and Britain out of our sincere desire to ensure Japan's self-preservation and the stablilization of East Asia, it being far from our thought either to infringe upon the sovereignty of other nations or to embark upon territorial aggrandizement. . . . However, it is according to the dictate of time and fate that we have resolved to pave the way for a grand peace for all the generations to come by enduring the unendurable and suffering what is insufferable."

A month later, Hirohito asked for and was granted an audience with Gen. Douglas MacArthur, the Allied commander in occupied Japan. Simply requesting such a meeting was an extraordinary act for Hirohito, a man regarded as a demigod, whose very name and visage struck awe in the hearts of Japanese.

At the time, the Soviet Union and Australia were demanding that Hirohito be tried as a war criminal. Millions of Americans considered Hirohito and the prime minister, Gen. Hideki Tojo, directly responsible for the war. And MacArthur's senior aides were urging the general to humiliate the emperor.

But MacArthur demurred, reasoning that to humble Hirohito would "outrage the feelings of the Japanese people and make a martyr of the emperor in their eyes." Unstated was MacArthur's intention to employ Hirohito's prestige to accomplish his goals during the occupation years.> Although the so-called Peace Constitution drafted for Japan under MacArthur's orders stripped the emperor of all his powers, making him subservient to "the will of the people with whom resides sovereign power," the new charter didn't really take effect until the occupation ended in 1952, according to historian Hata.

"Until then," he said, "the emperor effectively negotiated the future course of the country."

After that, Hirohito's stature shrank to a purely ceremonial level. Until illness weakened him, he spent his time participating in some 200 Shinto religiousrites and 50 public ceremomies each year.

In January 1924, Hirohito married Princess Nagako, whom he'd first seen from a distance at the imperial palace school when he was 10 and she eight. The couple had been engaged for seven years, during which they'd been allowed to meet nine times, and never alone.

After the war, he never again donned a military uniform or was seen astride a horse. His photographs more often than not showed him at his microscope or strolling, in rumpled clothes and panama hat, alongside the empress in a garden.