Tens of thousands of well-wishers gathered outside Japan's moat-ringed Imperial Palace _ many shouting "Banzai," a traditional wish for long life _ to mark Thursday's 20th anniversary of Emperor Akihito's coronation to the world's oldest throne.
Parades, concerts and speeches by leading athletes, actors, businesspeople and politicians marked the festivities that lasted most of the day.
But in unusually somber comments of his own, Akihito appealed for future generations to learn from the war-marred reign of his father, the late Emperor Hirohito.
In a rare news conference before the anniversary, the 75-year-old monarch said he is concerned that Japanese will forget their past.
Japan's Chrysanthemum Throne _ the world's oldest hereditary monarchy _ has undergone major changes since the country's surrender ended World War II in 1945, when Hirohito was officially considered a living god and loyalty to the throne was used to rally the nation behind the war.
Hirohito renounced his divinity under the Allied occupation and his role was redefined as that of a ceremonial symbol of the unity of the nation, without significant political powers.
Historians' views differ on exactly how much of a role Hirohito played in the war, but generally agree it was more often the generals, admirals and politicians who made the major decisions that set the country's disastrous course.
Akihito and his wife, Empress Michiko, 74, have grown quietly into the monarchy's new role, presiding over rituals at the palace shrines, giving out awards, meeting foreign dignitaries and swearing in new Cabinets.
They assumed the throne nearly a year after Hirohito's death on Jan. 7, 1989 because the nation was officially in mourning.
The soft-spoken, graying Akihito said he is striving to live up to his postwar responsibilities as a national symbol. But he said he also hopes Hirohito's legacy will not be misunderstood by future generations, noting that three out of four Japanese alive today were born after the war.
Japan invaded Manchuria six years after Hirohito ascended the throne, setting the course for its broader invasion of China and other parts of Asia. It had already occupied Korea.
"The reign of my father began at a very difficult time," Akihito said, adding that his father was "reluctant" about the events that led to war. "He viscerally knew the importance of peace."
"What worries me most is that the history of the past will gradually be forgotten," he said.
Japan has often been criticized by its neighbors _ who bore the brunt of Japanese colonialism _ for whitewashing its role in World War II in its school textbooks. Although Akihito has visited China, he has yet to travel to South Korea, largely because of lingering animosities over the war.
Akihito, who was 11 years old when the war ended, did not go into further detail in his pre-anniversary remarks, made last week. His public comments are famously circumspect, avoiding subjects that might have political implications.
But in remarks at a government-sponsored celebration Thursday, he also mentioned his contrition over the war.
"Some 3.1 million Japanese died in the war, and many lives of foreigners were also lost," he said. "We must not forget that today's Japan is built on those many sacrifices of the past."
Hirohito remained a controversial figure until his death and opposition to the monarchy was strong among some, particularly those groups _ including leftists, Christians and Buddhists _ that were most oppressed by the wartime government.
Akihito, however, is seen as a much more neutral figure, and the monarchy is generally respected by the nation _ though without the fervor that was expected of past generations.
In sharp contrast with Hirohito's funeral, when leftist radicals held large protests and torched Shinto shrines around the city, no incidents were reported Thursday, though security around the palace was tight.
Ben-Ami Shillony, a professor of East Asia studies at the University of Jerusalem and well-known expert on the Japanese monarchy, said that although it is good Akihito is a less divisive figure than his father was, he is also seen as less relevant by many and needs to find a cause to champion if he is to raise his public profile.
"He is the head of the oldest dynasty in the world," he said. "As the highest-ranking monarch, it is important for him to do something for a worthy cause. Supporting the emperor is not that popular in Japan, especially among the young."
Even so, officials said more than 50,000 people gathered around the Imperial Palace for a parade, a concert and other anniversary events. Prime Minister Yukio Hatoyama closed one of the main celebrations with three cheers of "Banzai."
Although he has been treated for cancer and other ailments, Akihito said in his news conference he is in good health and hopes to continue his duties.
According to traditional count, Akihito is the 125th in a line of emperors that began with Jimmu in 660 BC. Historical records suggest the throne dates back to at least the fifth century.