It was midday in Tokyo when Prime Minister Hideki Tojo announced to his countrymen and to the world that a few hours earlier Japan had struck the first blow and was now at war with the United States and Britain.

When he had finished, the historian John Toland has noted, the national radio broadcast a recording of an old martial air containing this stanza:

"Across the sea, corpses in the water;

Across the mountain, corpses in the field.

I shall die only for the emperor,

I shall never look back."

At that hour, the imperial forces of Japan were at work over vast areas of the Pacific. Thousands of miles to the east they had left an American fleet in ruins in the bloodied waters of Pearl Harbor; 3,600 Americans were dead or wounded. In the south, Japanese infantry stormed ashore in Malaya, now part of Malaysia, for a back-door assault on the British fortress at Singapore.

Singapore's governor, Sir Shenton Thomas, was awakened at his home and given the news. He remained complacent: "Well, I suppose you'll shove the little men off." Two hours later Japanese troops landed unopposed in Thailand.

Before the "day of infamy" -- Dec. 7, 1941 -- had ended, the emperor's "little men" had bombed Singapore, Hong Kong and Manila; had virtually destroyed American air power in the Philippines and had begun their assaults on the most important outposts of the United States in the central Pacific -- Guam, Wake and Midway islands.

A conflict of savagery unsurpassed in the history of human warfare had begun. By the time this war had run its course -- 40 years ago this Wednesday -- corpses were spread across all the fields and waters of the vast Pacific basin. Well over 3 million Asians, Americans and Europeans were dead; another 2.5 million were wounded. Had the American invasion of Japan gone forward as planned in late 1945, another million or 2 million corpses might have been added to the heap.

In the four decades that have gone by, memories of the war have become indistinct and mythologized in the popular culture. The official and emotional reconciliation between Japan and the United States is so firmly established that neither government has seen a need for a joint commemoration of this historic day as was held in West Germany in May on the anniversary of V-E Day. Indeed, as the years have passed, Japan, because of the Hiroshima and Nagasaki bombings, is seen in some quarters in the United States less as an aggressor and more as a victim of the war.

None of this, however, can erase the searing realities of those years between 1941 and 1945. Such deep hatreds, with strong racial overtones, were aroused that the conflict became, as the Japanese military planner Ishiwara Kanji had long predicted, a "war of annihilation."

Civilian populations were slaughtered by the hundreds of thousands as a matter of conscious and deliberate military policy on both sides. Prisoners of war were tortured or shot routinely.

Some Japanese units performed rituals of cannibalism on their prisoners; liver soup was one delicacy. Unrestricted submarine warfare, denounced as barbarous in the 1930s, became a standard military tactic. All ships -- civilian and military -- were fair game. Surviving passengers and crewmen were often machine-gunned as they floundered in the sea.

Flame throwers that produced "crispy little critters" in the Pacific islands were beloved by the infantrymen. The ethic of the battle was articulated by President Harry S Truman following the nuclear attack on Nagasaki: "When you deal with a beast, you have to treat him as a beast." There is little doubt he spoke for the country.

A New York Times correspondent was an official observer on the Nagasaki mission. He made these notes: "Does one feel any pity or compassion for the poor devils about to die? Not when one thinks of Pearl Harbor and of the Death March on Bataan." And not when they thought of the terrible fighting that had gone before -- Guadalcanal, New Guinea, Tarawa, Saipan, Guam, Peleliu, New Britain, Iwo Jima and Okinawa. Blend of Emotions

A few days after the war began, a Japanese military publicist issued a statement to the newspaper Asahi Shimbun. "Japan," he declared, "is the sun that shines for world peace. Those who bathe in the sun grow and those who resist it shall have no alternative but ruin. Both the United States and Britain should contemplate the 3,000 years of scorching Japanese history . . . . The general situation of war has been determined. The ultimate victory will be ours."

In the United States, the immediate reaction to the events unfolding was a curious blend of emotions. There was the predictable anger a Japanese correspondent encountered in Washington just hours after the Pearl Harbor attack. A cab driver shouted at him: "God damn Japan. We'll lick the hell out of those bastards now."

Among the pacifists and isolationists, there was the peculiarly American attitude of skepticism and disbelief.

On the afternoon of Dec. 7, long after the Pearl Harbor news had been received, Republican Sen. Gerald P. Nye of North Dakota, an ardent isolationist, addressed an America First rally in Pittsburgh, denounced president Franklin D. Roosevelt as a warmonger and made no mention of the day's events.

An Army colonel rose and demanded of the speaker: "Do you know that Japan has attacked Manila, that Japan has attacked Hawaii?" The crowd booed and threatened him.

On the following day Roosevelt asked Congress for a declaration of war, but even then doubters remained. Rep. Jeannette Rankin (R-Mont.), an ally of Sen. Nye, cast the only negative vote, saying that "it might all be a mistake, it might be propaganda. How did Congress know for sure that Hawaii had been attacked? It might be a presidential ruse. There's so much propaganda nowadays."

But these were aberrational voices. Correspondents for Time magazine conducted man-on-the-street interviews in many cities, finding that people were calm, unafraid and ready for the hard work ahead: "Well, it's here." "We're in it and we'll just have to make the best of it." "Those Japs must be crazy."

And there was an almost universal sense of confidence that the war would be won. The comedian Bert Wheeler stood up in a restaurant and sang an instant ballad composed in Hollywood:

"The flag flies high, so do or die, America.

Let's stand together today,

In that old American way.

. . . And make those cowards pay."

Hollywood even produced instant humor: "If Los Angeles ever had an air raid, the people probably wouldn't pay any attention to it. They'd think it was just another Hollywood preview." The Japanese Advance

There was little to inspire humor in the months that followed. Germany and Italy declared war on the United States.

In the Pacific, Japanese forces seemed invincible. They occupied Vietnam and its great French naval base at Cam Ranh Bay. Thailand, Laos, Singapore, Malaya, Hong Kong and the Dutch West Indies, now Indonesia, were seized, finishing the British and Dutch as significant factors in the war and providing Japan with desperately needed resources, including oil.

Burma was tottering. Australia, New Zealand and India were terrified by their vulnerability. Korea, Taiwan and vast areas of China were in Japanese hands.

En route to the Philippines, Japanese assault troops were informed of their mission: "To free a hundred million Asians tyrannized by 300,000 whites." By May 1942 they had forced the humiliating surrender of American forces; a Marine regiment raised the white flag for the first time in the history of the corps. Gen. Douglas MacArthur was forced to flee to Australia. The islands of Guam and Wake were overrun. Japanese outposts were established all across the central Pacific Ocean, creating a defensive chain of great strategic value.

The summer of 1942 was now at hand, a season, whatever the forebodings in the United States, that was to be the high-water mark of the Japanese Empire and its dreams of hegemony in the Pacific and the Far East. It was the season of "decisive battle." This concept was at the heart of Japanese military doctrine. It envisioned the coming together of great forces for a mad moment of battle in which, inevitably, the enemy would be mortally wounded and his will to fight would be destroyed.

The Japanese that summer suffered from what historian John Costello has called the "victory disease." They believed, with the strategist Kanji, that "the Japanese armed forces are the guardian deity of . . . righteousness -- the Japanese kokutai spiritual uniqueness -- which shall save the world." Emperor Hirohito presciently recognized the dangerous symptoms of this hubris: "The fruits of victory are tumbling into our mouths too quickly." But leading military figures disagreed.

Adm. Isoroku Yamamoto, who planned and executed the brilliant strike on Pearl Harbor, insisted that the summer of 1942 would see the "decisive battle," a battle that would give Japan unchallenged control of the great ocean, would open the way for the capture of Hawaii and force the Americans to sue for peace.

It would be fought in the warm and lovely coral-green waters around Midway Island. He would assemble a great fleet, lure the Americans into a fight and destroy the remnants of the American Navy that had survived the Pearl Harbor disaster. Midway would be occupied, and the Aleutian Islands off the American mainland would become outposts of Japanese power.

Japanese confidence was so high that a new name had already been chosen for Midway: The Island of the Rising Sun. Yamamoto embarked his fleet of battleships, cruisers, carriers, destroyers and supporting vessels late in May. They were bound not for victory but for a disaster that changed the entire course of the Pacific war.

Long before his task force reached Midway, the Japanese codes had been broken. American intelligence officers were able to tell their Pacific commander, Adm. Chester Nimitz, confidently: "They'll come in from the northwest on a bearing 325 degrees and they will be sighted at about 175 miles from Midway . . . . The time will be 06:00."

A high-risk ambush was ordered. In the entire Pacific Ocean, Nimitz had only three aircraft carriers: the Enterprise, Hornet and Yorktown, which had been severely damaged in the Battle of the Coral Sea a few weeks earlier. All three were committed to the task force that set out for Midway on May 28 under the command of Rear Adm. Raymond Spruance.

A week later the trap was sprung. Before the sun had set that day -- June 4 -- American pilots, flying inferior aircraft, had broken the back of Yamamoto's great fleet. The Japanese lost four huge carriers, a heavy cruiser, 234 aircraft and 2,200 sailors. Their finest carrier pilots were wiped out.

Dismayed and depressed, Yamamoto ordered his surviving ships to retreat to Japan. From that day until the end of the war, Japanese forces never again gained the offensive.

The U.S. Navy's commander, Adm. Ernest King, made an accurate assessment of the Midway engagement: It "was the first decisive defeat suffered by the Japanese Navy in 350 years . . . . It put an end to the long period of Japanese offensive action, and restored the balance of naval power in the Pacific." It put an end to the myth of Japanese naval invincibility, and three months later the myth of the Japanese Army's invincibility was destroyed on Guadalcanal in the Solomon Islands.

The island was occupied early in August by the 1st Marine Division. The Japanese considered Guadalcanal vital to their strategic situation and, during the next six months, committed more than 40,000 troops to its capture. More than 23,000 of them died before the effort was abandoned and the survivors were withdrawn.

Japanese Adm. Raizo Tanaka later wrote: "There is no question that Japan's doom was sealed with the closing struggle for Guadalcanal. Just as it betokened the military character and strength of her opponent, so it presaged Japan's weakness and lack of planning that would spell her military defeat."

In one of the postwar movie versions of the Pearl Habor raid, a Japanese admiral warns his colleagues: "We have awakened a sleeping giant." The image was appropriate.

The year before the war began, the United States had 458,000 men under arms; that number had grown to nearly 4 million by the end of 1942 and to more than 12 million by 1945.

When America's factories switched to a wartime basis, the results were remarkable. Detroit, in 1941, had produced 3.8 million passenger cars. In 1943 exactly 139 passenger cars came off assembly lines that by then were turning out tanks and other military vehicles by the millions. Military aircraft production soared from 6,000 planes in 1940 to nearly 50,000 in 1942 and to nearly 100,000 by 1944. The tonnage of merchant vessels produced in American shipyards was 193,000 in 1940 and 10.5 million in 1943.

Thus, despite the demands of a two-front war, there were to be no shortages of men or materiel. By the end of 1942 more than 280,000 U.S. troops were in the Pacific, and a year later there were nearly 2 million.

On paper, Japan still enjoyed an enormous manpower advantage, with 7 million men under arms at the beginning of the war. But the numbers are misleading. Japanese forces were dispersed all over East and South Asia, in Japan's own home islands and in dozens of outposts extending across the Pacific all the way to the Aleutians.

Japan, moreover, lacked the industrial base and the resources necessary for a protracted war of attrition. Ishiwara Kanji summed up the problem early in the war: "Inevitably, we shall lose this war. It will be a struggle in which Japan, even though it has only a thousand yen in its pocket, plans to spend 10,000, while the United States has 100,000, but only needs to spend 10,000 . . . . We simply cannot last . . . . Japan started this war without considering its resources beforehand."

All through 1943, freshly equipped ground, air and naval forces poured into the Pacific from the United States. Strategically important bases in the southwest Pacific, including New Guinea and the Solomon Islands, were secured. Tarawa and Makin in the Gilbert Islands chain in the central Pacific were taken late in the year.

The 72-hour Tarawa battle shocked Americans at home because of the heavy U.S. Marine casualties. But all this was merely a prelude to the great American offensive in the Pacific in 1944 and early 1945. By the end of 1944 Japanese outposts in the central Pacific had been either eliminated or made useless by their isolation: the Marshall Islands, the Marianas and Peleliu in the Palaus were seized, giving the United States air bases for the bombing of Japan. American naval forces decimated the Japanese fleet in battles near the Marianas and in Leyte Gulf. In October, the 10th Army began the reconquest of the Philippines.

The final year of the war opened with two of the most fierce and costly engagements in the history of the American military -- the capture of Iwo Jima and Okinawa. American losses totaled 75,000 dead and wounded. Japan lost nearly 140,000 men.

The Iwo Jima battle, perhaps more than any engagement of the war, had enormous resonance among the American people. It fixed forever in their minds the heroism and fighting qualities of their sons and brothers and husbands; it fixed forever in their minds the terrible costs and hardships of war.

The photograph of the American flag-raising on Mount Suribachi came to symbolize those qualities and sacrifices, not only for the marines on the island, but for all American servicemen. It inspired a confidence in the the capabilities of the armed forces that lasted through the two decades leading up to the Vietnam War. Political Impact in U.S.

The war, and some of these Pacific battles in particular, also had long-lasting political resonance in the United States. Every American president since Truman has been identified in one way or another with World War II, and five of them -- John F. Kennedy, Richard M. Nixon, Lyndon B. Johnson, Gerald Ford and Jimmy Carter -- were young Navy officers. All but Carter saw service in the Pacific.

As the Okinawa battle wound down, the strategic bombing of Japan was intensified. Before it was over, 169 square miles of 66 cities were destroyed. The Japanese counted 260,000 killed, 412,000 injured and 9.2 million people left homeless by the incendiary attacks of the American B29s, not counting casualties in Hiroshima and Nagasaki.

Simultaneously, planning for the invasion of the Japanese home islands proceeded rapidly. The operation would begin on Nov. 1, 1945, with the invasion of the southern island, Kyushu, by 13 Army and Marine divisions totaling 780,000 men. Four months later, 25 additional divisions would land on the main island of Honshu.

The Japanese in the summer of 1945 were in desperate straits but the militarists in control of the government were prepared for the empire's "final battle." They had available in the home islands 10,000 aircraft, 2,350,000 regular troops and 32 million people in "civilian militias," many of them armed with nothing more than sharpened bamboo spears, ancient rifles and shotguns.

The prospect of the invasion was horrifying to many American commanders. The recent fighting on Iwo Jima and Okinawa had demonstrated again the tenacity of the Japanese. On the home islands, American troops would encounter not only the Japanese armed forces but millions of civilians prepared to die for the emperor. Casualty estimates on the American side alone exceeded 1 million. The ultimate price the two countries would have paid never will be known.

On Aug. 6, a nuclear weapon was dropped on Hiroshima, destroying 60 percent of the city; between 70,000 and 100,000 people were killed and 70,000 were injured. A second nuclear bomb was dropped on Nagasaki on Aug. 9, causing similar destruction. The day before, the Soviet Union had launched a surprise attack on Japanese forces in Manchuria. More than 1 million Soviet troops, 5,000 tanks and 5,000 aircraft were involved in the assault.

Five days later Emperor Hirohito recorded a speech for broadcast to the nation. It was a formal offer of surrender.

"The war situation," he said, "has developed not necessarily to Japan's advantage, while the general trends of the world have all turned against her interest. Moreover, the enemy has begun to employ a new and most cruel bomb, the power of which to do damage is indeed incalculable . . . . This is the reason we have ordered" the surrender.

He continued, "Unite your total strength to be devoted to the construction for the future. Cultivate the ways of rectitude; foster nobility of spirit; and work with resolution so as ye may enhance the innate glory of the imperial state and keep pace with the progress of the world."

Among American troops preparing to embark for the Kyushu invasion -- most of them in their teens and early twenties -- an old English battle prayer was recalled:

"Oh, Lord, Thou knowest how busy I must be this day.

If I forget Thee, do not Thou forget me."

The prayer could now be left unsaid. The Pacific war had ended. The boys were going home to assume the humble lives many had known and in other cases to assume the leadership of their country as politicians, corporate managers, scientists, scholars, university presidents and as professional warriors.

The United States was a new country. It had emerged from isolationism and economic stagnation to become the most powerful nation on earth, a nation with domestic and international interests, commitments and entanglements that are with us yet.

That new country, 40 years old today, is the gift to sons and daughters from the boys and the young men who went off to strange-sounding places in the Pacific and Europe in dark days long ago.