August 6, 1945: America Drops Atomic Bomb on Hiroshima, Nuclear Age Begins

The fall of 1939 saw dramatic changes in world events that would alter the course of history. On September 1, 1939, Nazi Germany invaded Poland to trigger the start of World War II but imperial Japan had been ravaging Manchuria and China for nearly a decade. Even though the United States was officially neutral in the world war, President Franklin Roosevelt had an important meeting in mid-October.

Roosevelt met with his friend, Alexander Sachs, who hand-delivered a letter from scientists Albert Einstein and Leo Szilard. They informed the president that German scientists had recently discovered fission and might possibly be able to build a nuclear bomb. The warning prompted Roosevelt to initiate research into the subject and beat the Nazis.

The United States entered the war after Japan bombed Pearl Harbor on December 7, 1941, and the Roosevelt administration began the highly secretive Manhattan Project in October 1942. The project had facilities in far-flung places and employed the efforts of more than half a million Americans across the country. The weapons research laboratory resided in Los Alamos, New Mexico, under the direction of J. Robert Oppenheimer.

As work progressed on a nuclear weapon, the United States waged a global war in the Pacific, North Africa, and Europe. The Pacific witnessed a particularly brutal war against Japan. After the Battle of Midway in June 1942, the Americans launched an “island-hopping” campaign. They were forced to eliminate a tenacious and dug-in enemy in heavy jungles in distant places like Guadalcanal. The Japanese forces gained a reputation for suicidal banzai charges and fighting to the last man.

By late 1944, the United States was closing in on Japan and invaded the Philippines. The U.S. Navy won the Battle of Leyte Gulf, but the Japanese desperately launched kamikaze attacks that inflicted a heavy toll, sinking and damaging several ships and causing thousands of American casualties. The nature of the attacks helped confirm the Americans believed they were fighting a fanatical enemy.

The battles of Iwo Jima and Okinawa greatly shaped American views of Japanese barbarism. Iwo Jima was a key island for airstrips to bomb Japan and U.S. naval assets as they built up for the invasion of Japan. On February 19, 1945, the Fourth and Fifth Marine Divisions landed mid-island after a massive preparatory bombardment. After a dreadful slog against an entrenched enemy, the Marines took Mt. Suribachi and famously raised an American flag on its heights.

The worst was yet to come against the nearly 22,000-man garrison in a complex network of tunnels. The brutal fighting was often hand-to-hand. The Americans fought for each yard of territory by using grenades, satchel charges, and flamethrowers to attack pillboxes. The Japanese fought fiercely and sent waves of hundreds of men in banzai charges. The Marines and Navy lost 7,000 dead and nearly one-third of the Marines who fought on the island were casualties. Almost all the defenders perished.

The battle for Okinawa was just as bloody. Two Marine and two Army divisions landed unopposed on Okinawa on April 1 after another relatively ineffective bombardment and quickly seized two airfields. The Japanese built nearly impregnable lines of defense, but none was stronger than the southern Shuri line of fortresses where 97,000 defenders awaited.

The Marines and soldiers attacked in several frontal assaults and were ground up by mine fields, grenades, and pre-sighted machine-guns and artillery covering every inch. For their part, the Japanese launched several fruitless attacks that bled them dry. The war of attrition finally ended with 13,000 Americans dead and 44,000 wounded. On the Japanese side, more than 70,000 soldiers and tens of thousands of Okinawan civilians were killed. The naval battle in the waters surrounding the island witnessed kamikaze and bombing attacks that sank 28 U.S. ships and damaged an additional 240.

Okinawa was an essential staging area for the invasion of Japan and additional proof of the fanatical nature of the enemy. Admiral Chester Nimitz, General Douglas MacArthur, and the members of the Joint Chiefs of Staff were planning Operation Downfall—the invasion of Japan—beginning with Operation Olympic in southern Japan in the fall of 1945 with fourteen divisions and twenty-eight aircraft carriers, followed by Operation Coronet in central Japan in early 1946.

While the U.S. naval blockade and aerial bombing of Japan were very successful in grinding down the enemy war machine, Japanese resistance was going to be even stronger and more fanatical than Iwo Jim and Okinawa. The American planners expected to fight a horrific war against the Japanese forces, kamikaze attacks, and a militarized civilian population. Indeed, the Japanese reinforced Kyushu with thirteen divisions of 450,000 entrenched men by the end of July and had an estimated 10,000 aircraft at their disposal. Japan was committed to a decisive final battle defending its home. Among U.S. military commanders, only MacArthur underestimated the difficulty of the invasion as he was wont to do.

Harry Truman succeeded Roosevelt as president when he died on April 12, 1945. Besides the burdens of command decisions in fighting the war to a conclusion, holding together a fracturing alliance with the Soviets, and shaping the postwar world, Truman learned about the Manhattan Project.

While some of the scientists who worked on the project expressed grave concerns about the use of the atomic bomb, most decision-makers expected that it would be used if it were ready. Secretary of War Henry Stimson headed the Interim Committee that considered the use of the bomb. The committee rejected the idea of a demonstration or a formal warning to the Japanese in case it failed and strengthened their resolve.

On the morning of July 16, the “gadget” nuclear device was successfully exploded at Alamogordo, New Mexico. The test was code-name “Trinity,” and word was immediately sent to President Truman then at the Potsdam Conference negotiating the postwar world. He was ecstatic and tried to use it to impress Stalin, who impassively received the news because he had several spies in the Manhattan project. The Allies issued the Potsdam Declaration demanding unconditional surrender from Japan or face “complete and utter destruction.”

After possible targets were selected, the B-29 bomber, Enola Gay, carried the uranium atomic bomb nicknamed Little Boy from Tinian Island. The Enola Gay dropped Little Boy over Hiroshima, where the blast and resulting firestorm killed 70,000 and grievously injured and sickened tens of thousands of others. The Japanese government still adamantly refused to surrender.

On August 9, another B-29 dropped the plutonium bomb Fat Man over Nagasaki which was a secondary target. Heavy cloud cover meant that the bomb was dropped in a valley that restricted the effect of the blast somewhat. Still, approximately 40,000 were killed. The dropping of the second atomic bombs and the simultaneous invasion of Manchukuo by the Soviet Union led to the Emperor Hirohito to announce Japan’s surrender on August 15. The formal surrender took place on the USS Missouri on September 2.

General MacArthur closed the ceremony with a moving speech in which he said,

It is my earnest hope, and indeed the hope of all mankind, that from this solemn occasion a better world shall emerge out of the blood and carnage of the past—a world founded upon faith and understanding, a world dedicated to the dignity of man and the fulfillment of his most cherished wish for freedom, tolerance, and justice…. Let us pray that peace now be restored to the world, and that God will preserve it always. These proceedings are closed.

World War II had ended, but the Cold War and atomic age began.

Tony Williams is a Senior Fellow at the Bill of Rights Institute and is the author of six books including Washington and Hamilton: The Alliance that Forged America with Stephen Knott. Williams is currently writing a book on the Declaration of Independence.

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