Before World War II, the US was a Pacific power

Japan's imperial expansion in Asia in the 1930s set the stage for war with the US.

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The US Pacific strategy sought control of key islands to close in on Japan

The US adopted a two-pronged "island hopping" campaign across the Central and Southwest Pacific from 1943–44, deliberately targeting strategically crucial but less-defended islands. This allowed forces to bypass heavily fortified Japanese strongholds and build airfields for bombers aimed at Japan, drastically accelerating the path toward Tokyo while conserving manpower and resources.

Before Pearl Harbor, the US was a nonbelligerent ally to the Allied powers

Between September 1940 and December 7, 1941, the United States remained officially neutral—yet President Roosevelt incrementally shifted policy from “cash‑and‑carry” to Lend‑Lease, funneling critical military aid to Britain and other allies without entering the war.

Hitler declared war on the United States four days after Pearl Harbor

Despite having no treaty obligation to join Japan’s fight, Hitler declared war on the US on Dec. 11, 1941. The move pulled America into the European theater and is widely seen as one of Hitler’s most strategic blunders.

Japan attacked Pearl Harbor largely because it was running out of oil

This video traces how US-led sanctions and Japan’s near-total dependence on imported oil pushed Japanese leaders toward a high-risk plan: seize Southeast Asian oil fields and neutralize the American Pacific Fleet, hoping Washington would negotiate rather than fight.

The US asked Japan to leave China less than two weeks before Pearl Harbor

On Nov. 26, 1941, Secretary of State Cordell Hull issued a note calling on Japan to withdraw from China and Indochina—terms Tokyo saw as impossible. The note confirmed to Japanese leaders that diplomacy had collapsed, accelerating plans for the Pearl Harbor strike (which had been formally approved Nov. 5).

Japan's attack on Pearl Harbor caused heavy losses but failed to cripple the US navy

Japan’s air assault sank or damaged 18 warships (including eight battleships) and destroyed 188 aircraft, killing 2,403 Americans, yet all three Pacific Fleet aircraft carriers were absent and survived, and vital infrastructure like oil depots and repair yards remained intact—preserving core US naval power and enabling a rapid recovery. Watch original reporting here.

What happened to Americans who were in Japan during Pearl Harbor?

When Japan bombed Pearl Harbor in December 1941, roughly 10,000 American civilians were stranded in Japanese-occupied territory. Tense diplomatic negotiations eventually secured two prisoner exchanges conducted via ship across 20,000 nautical miles to return nearly 3,000 Allied civilians, while Japanese Americans in North and South America were sent in the opposite direction, many to a country they had never called home.

The Pearl Harbor attack led to the mass internment of Japanese Americans

In the months after Pearl Harbor, the US forcibly removed and incarcerated about 120,000 Japanese Americans—two-thirds of them citizens. Driven by fear and racism, the policy is now recognized as a grave violation of civil rights.

See a visualization of the Japanese attack on Pearl Harbor.

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The Battle of Midway flipped the balance of power in Pacific naval dominance

Between June 4–7, 1942, U.S. carrier-based aircraft, aided by broken Japanese codes and radar detection, ambushed and sank all four Japanese fleet carriers while losing only one, decisively undermining Japan's offensive capacity and marking the turning point in the Pacific War.

Japan had the world's best carrier aviation in 1941

In late 1941, Japan possessed the world’s most powerful carrier fleet and the best-trained naval aviators, giving it a short-term edge over the US. But Japan couldn’t replace ships or pilots quickly, and US industry would soon outbuild it.

See how newspapers broke the news of the attack around the world

This collection showcases front pages from cities around the globe reacting to Pearl Harbor in real-time—capturing the shock, fear and uncertainty as the US entered World War II.

US intelligence failures contributed to the success of the Japanese attack

Despite breaking Japan’s diplomatic codes, US agencies failed to integrate warnings, successfully track Japan’s carriers, or even believe a Hawaii strike was possible (they also had not cracked Japan’s naval codes). Missed signals, ignored reports and poor coordination led to one of the worst intelligence failures in US history.

Roosevelt’s post-Pearl Harbor address became one of America’s most iconic speeches

Delivered to a joint session of Congress on Dec. 8, 1941, President Franklin D. Roosevelt declared Dec. 7 “a date which will live in infamy.” The speech, heard by tens of millions of Americans, helped consolidate national support for entering the war.

The attack at Pearl Harbor required nearly a year of planning and preparation

In early 1941, Admiral Isoroku Yamamoto ordered detailed planning for a surprise carrier strike on Pearl Harbor. Japanese teams spent months refining torpedo modifications, training pilots, and rehearsing the complex attack.

Okinawa’s ferocity convinced the US atomic bombs was necessary

The brutal 82-day Battle of Okinawa—where US forces suffered nearly 50,000 casualties and Japanese military and civilians lost over 200,000 lives—clinched the grim reality that a full invasion of Japan would be even bloodier. This stark lesson directly shaped American decisions to deploy atomic weapons, aiming to avoid a potentially catastrophic ground war on the Japanese mainland.

Hawaii lived under martial law for nearly three years after Pearl Harbor

After the attack, Hawaii was placed under sweeping military rule—curfews, censorship, warrantless arrests, ID papers, and mass detentions transformed everyday life. More than 2,000 people were arrested within 48 hours of the attack, and the islands remained under martial law for nearly three years.

Franklin D. Roosevelt's 1941 speech framed World War II as a global fight for universal rights

Eleven months before the attack on Pearl Harbor, President Roosevelt outlined four fundamental freedoms that, in his words, people "everywhere in the world" ought to enjoy—speech, worship, freedom from want, and freedom from fear.

When German submarines lurked in US coastal waters

During World War II, German submarines (also known as U-boats) prowled the Southern coast of the US in 1942 and 1943, sinking more than 60 ships and killing 600 Allied soldiers. The campaign is less well-known, since the major battles in Stalingrad and Midway happened at the time. Several of these submarines and the ships they sank are now popular diving spots.

The attacks prompted a quick jump in American public support for war

In a Gallup poll taken days after the attack, an extraordinary 97% of Americans approved Congress declaring war on Japan—reflecting overwhelming national unity in the wake of the strike.

The Pearl Harbor attack was influenced by a British raid on Italian battleships

Japan closely studied Britain’s 1940 attack at Taranto, where carrier-launched torpedo planes crippled Italian battleships in shallow water. Although Japanese planning for Pearl Harbor was already underway, Taranto demonstrated the plan’s feasibility and strengthened Japanese confidence that a surprise carrier assault could cripple the US Pacific Fleet.

How the US entered WWI in 1917

Originally taking a position of neutrality during the course of World War I, the United States of America eventually relented. Entering the war in 1917, support for the British and French had risen and Americans were incensed by Germany's overtures to Mexico and U-boat attacks that sank ships and ended American lives. See how and why the US entered WWI in this article.

The US used military pressure to force Japan to open to foreign trade in the 1850s

Commodore Matthew Perry arrived in Edo Bay (now Tokyo Bay) with heavily armed warships, pressuring Japan to open its ports. His expeditions led to the 1854 Treaty of Kanagawa, which opened two ports for supplies and established formal US-Japan relations. Full commercial trade followed later under the 1858 Harris Treaty.

The Panama Canal boosted the US as a world power in trade, engineering, and finance

The effort proved the US could achieve grand engineering projects while granting it influence over (and benefitting economically from) a major interoceanic channel and its host country, Panama.

Wartime conferences exposed cracks in the US–Soviet alliance

At the Tehran, Yalta and Potsdam Conferences, Allied leaders coordinated WWII strategy—but deep disagreements over postwar Europe foreshadowed the Cold War. The USSR’s push for influence in Eastern Europe clashed with US and British calls for self-determination.

The Monroe Doctrine helped lead to the American occupation of territory abroad

This podcast explores how the policy motivated a century of US military intervention throughout Latin America, the Caribbean, and the Pacific—covering the annexation of Hawaii, the Spanish-American War, and occupations of Cuba, Haiti, and Panama.

The formation of the UN elevated the US on the world stage

This podcast episode of "To the Best of My Ability" from the National WWII Museum goes behind the scenes of the United Nations' founding from the American perspective. It explores how FDR's vision for global peace took shape, how Truman carried it forward, and how Eleanor Roosevelt helped define human rights—set against the backdrop of wartime diplomacy, Cold War tensions, and the San Francisco Conference, where the UN Charter was signed.

See what it was like to live in the United States during World War II

In America, life was transformed by total war: sixteen million service members left civilian life, while massive industrial production demanded labor. Women, minorities, and teens filled factories, fueling boomtown growth and breaking social barriers. Simultaneously, rationing, recycling drives, Victory Gardens, ration stamps, blackout drills, and war bond campaigns permeated daily routines.

How two US Presidents defined WWII and its aftermath

The National WWII Museum’s “To the Best of My Ability” podcast series delves into how Presidents Franklin D. Roosevelt and Harry S. Truman steered the US through World War Two.

World War II's Battle of Savo Island was the worst wartime naval defeat in US history

On Aug. 9, 1942, a larger, radar-equipped Allied fleet lost four heavy cruisers off Guadalcanal in the Pacific theater without sinking a single Japanese ship. The Navy kept the humiliating rout secret from the public for years. Experts argued failure resulted from fractured command, not inferior arms or ships.

Learn how Japan used the jet stream to launch attacks on US soil during World War II

In the final two years of the war, over 9,000 Fu-Go balloon bombs were launched from Japan, with about a thousand estimated to have reached North America. Six civilians killed by a Fu-Go bomb in Bly, Oregon, on May 5, 1945, became the only known deaths on American soil by enemy action during the war.

The perplexing Battle of Los Angeles in 1942 generated swaths of UFO conspiracies

On Feb. 24-25, 1942, weeks after the Pearl Harbor attack, a US military radar warned of enemy aircraft. A citywide blackout went into effect, powerful searchlights were lit up, and US forces fired artillery at what they believed to be the enemy. However, no confirmed enemy planes were ever identified. Eyewitnesses reported seeing large objects flying overhead, and much of the public speculated about UFOs and extraterrestrial attacks.

Comic books were a major part of American propaganda efforts during WWII

See how US comic books, alongside international counterparts, served as powerful wartime propaganda tools from 1941 to 1945—boosting morale, promoting war bonds, and demonizing Axis powers through the use of iconic heroes and patriotic messaging.

Should the US have entered into World War I?

America entered World War I in 1917, but had remained neutral until that point. President Woodrow Wilson addressed Congress, further underlining the USA's neutrality. Eleven weeks later, he asked for a declaration of war. With attacks by German saboteurs on an American munitions depot, it seemed he had no choice. But did he? This article asks what might have happened if the US stayed out of WWI.

The formal Japanese unconditional surrender that ended World War II took place on the deck of the USS Missouri in Tokyo Bay on Sept. 2, 1945.

FDR stayed composed as he absorbed the news of Pearl Harbor

This video reconstructs Roosevelt’s steady, methodical response on Dec. 7, 1941, from his first briefing to drafting his speech to Congress. It demonstrates how FDR maintained composure and moved rapidly to prepare the nation for war.

Japan was an empire from 1868 until 1947

The Empire of Japan began on Jan. 3, 1868, and facilitated rapid modernization. It endured through a period of colonial expansion—including Korea and Taiwan—1930s militarism, and participation in WWII, until Japan’s formal transformation into a constitutional state under the 1947 constitution following Allied occupation.

World War I brought attention to US reliance on mineral imports

Domestic stockpiles were inadequate for the extended trade disruptions caused by the four-year war. In response, the US Geological Survey increased its geological mapping to help search for important metals alongside new oil fields for fuel.

A single bomb on the USS Arizona killed 1,177 crew members in seconds

When a Japanese armor-piercing bomb triggered the explosion of the USS Arizona’s forward magazine during the attack, the blast killed 1,177 crew members within moments—accounting for nearly half of all American deaths at Pearl Harbor.

The Roosevelt Corollary transformed the Monroe Doctrine from a defensive warning into a rationale for US military intervention

In 1904, President Theodore Roosevelt declared that the US had the right to exercise international police power in Latin America. Over the following two decades, the US intervened militarily in the region about a dozen times—often enough that Marines became known locally as "State Department troops."

The Flying Tigers: American fighter pilots who fought for China in WWII

Read the story of the Flying Tigers, a unit of American pilots, many Chinese-Americans, hired by the Chinese in 1941 to fight the Japanese in the skies. While the US wasn't officially at war with Japan until later on, some of the earliest American "victories" over the Japanese were won by the Flying Tigers. Read more of this amazing bit of aviation history here.

The attack at Pearl Harbor led to the world's first around-the-world commercial flight.

The Japanese Navy used radio silence and deception to mask its approach

In late November 1941, Japan’s carrier strike force maintained total radio silence while operators back home broadcast normal traffic—creating ambiguity about the location of the fleet. The deception obscured US intelligence and helped create a surprise attack.

2 months after Pearl Harbor, American libraries launched a drive to collect 10 million books for soldiers

The 1942 Victory Book Campaign—sponsored by the American Library Association, the Red Cross, and the USO—asked the public to donate books to both train and entertain troops. The national campaign exceeded its goal, collecting more than 10.2 million books.

A downed Japanese pilot sparked a violent three-day standoff on the island of Niʻihau

After a Japanese pilot crash-landed on the Hawaiian island of Niʻihau, residents first sheltered him. Once news of the Pearl Harbor attack arrived, two locals tried to help him escape, leading to a violent struggle in which Native Hawaiians ultimately stopped and killed him.

The UK was already in a depression before the US Great Depression took hold

The US Great Depression was felt globally, but the severity and length of different countries’ economic downturns varied. For instance, Japan was the first country to exit its depression.

See images of shipwrecks from WWII's Battle of Midway

Deep-sea explorers have captured detailed images of three iconic shipwrecks from World War II's Battle of Midway, including the first up-close photos of the Japanese aircraft carrier Akagi since its sinking in 1942.

Questions about the US' commitment to its allies may have sparked a new nuclear age

Some US allies—from Warsaw to Seoul—are reevaluating their security amid doubts over American nuclear commitment, signaling the possibility they may want to acquire their own weapons.

The power and influence of the American presidency have expanded significantly over time—far beyond what the founders envisioned.