Japan’s imperial expansion in Asia set the stage for war with the US

Before World War II, the US was a Pacific power

Decades before Pearl Harbor, the US held major Pacific territories—Hawaii, the Philippines, Guam, American Samoa, and numerous island bases—giving it strategic reach across the western Pacific. This presence increasingly overlapped with Japan’s imperial ambitions in the region, contributing to rising tensions.

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).

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.

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.

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.

Japan committed mass war crimes during its invasion of China

During the 1937 invasion, Japanese forces carried out systematic atrocities—including mass executions, rape, torture, forced labor, and chemical warfare. The Nanjing Massacre alone killed tens of thousands over a span of six weeks, with some estimates claiming 300,000.

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.

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.

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.

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.

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.

President Polk deliberately provoked war with Mexico

After Mexico refused to sell California and New Mexico, President James K. Polk ordered US troops into disputed territory between the Nueces River and the Rio Grande—knowing it would likely spark a conflict. When fighting broke out, he used it to justify declaring war.

The 1967 war was the first use of oil as a geopolitical weapon

Following the June 1967 Arab–Israeli war, Saudi Arabia, Kuwait, Iraq, Libya, and Algeria embargoed oil shipments to the US, UK, and West Germany. While the move did not have a large impact, it reshaped global oil flows, and foreshadowed OAPEC's later actions.

A short history of the China-Taiwan conflict

The relationship between China and Taiwan is a fraught one, and has been for well over a century. US involvement has only raised the stakes between the independent island country, also known as the Republic of China, and the larger country on the mainland. Here's a breakdown of the conflict between China and Taiwan over the years.

World War I causes

World War I was, as the name says, truly war on the global scale. Fought between the French, Russian, British, Austria-Hungary, Ottoman, and Russian Empires, it was in part, a battle for territory. And after the war ended, several of these empires collapsed. Explore the different causes of World War II in this article.

US–Soviet hostility began long before the Cold War

US–Soviet tensions began decades before WWII. After the 1917 revolution, the US refused to recognize the Bolshevik regime and even sent troops to fight against it.

The “Phoney War” was an eight‑month build-up to war

From September 1939 to May 1940, following their war declaration on Germany, Britain and France entered a phase of military inaction—even as civil defence measures, naval blockades, and rationing intensified at home. Skirmishes were limited, but the decisive fighting didn't begin until Germany invaded Norway and France in April–May 1940, abruptly ending the uneasy stalemate.

A trade war is an economic conflict where nations impose tariffs or other trade barriers on each other in retaliation for similar actions

The US-China trade war is one example. While they aim to protect domestic industries, they can lead to higher prices for consumers and strained international relations.

China doubled its nuclear stockpile between 2020 and 2025, with plans for further expansion

China's arsenal grew from an estimated 300 warheads in 2020 to approximately 600 in 2025—making it the world's third-largest nuclear power. The US Department of Defense projects that China will surpass 1,000 warheads by 2030.

The 20th-century rise of fascism affected the World Cup

Spain, in the midst of a civil war, did not participate, and Japan, after invading China, pulled out of the competition. An additional six Central and North American teams scratched by the time that year's World Cup began.

The failed Bay of Pigs invasion led to the Cuban Missile Crisis, which brought the world to the brink of nuclear annihilation

Moscow's decision to deploy nuclear missiles in Cuba—just 90 miles from the US—pushed the world to the brink of nuclear war. To prevent future crises, both sides later set up a direct hotline and boosted arms-control diplomacy

The Chinese Exclusion Act was America's first major immigration restriction

The act, signed in 1882, barred Chinese laborers from entering the United States, marking the first significant restriction on free immigration. This overview examines 19th-century Chinese immigration, rising anti-Chinese sentiment, and the diplomatic implications of exclusionary legislation.

A trading company became Britain's most powerful imperial force

The East India Company began as a private merchant venture and grew into Britain’s dominant power in India—amassing wealth, fielding armies, and governing tens of millions until the Crown took direct control in 1858.

What led to the Vietnam War?

On the heels of gaining independence from colonizers, why did Vietnam fracture and begin its internal battle? Though the war took root during an independence movement against French colonial rule, it evolved into a Cold War confrontation with international support. This article explains six events that led to the conflict between North and South Vietnam.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

'Shogun,' a 1980s TV series, helped popularize sushi in the US by stimulating an American interest in Japanese culture.

The US dollar is the most widely circulated currency in the world, and is involved in nearly 90% of global transactions

Explore an interactive map of battles from the American Revolution, along with detailed summaries of each engagement

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

The Beatles' US label rejected the band's first two singles, 'Please Please Me' and 'From Me to You,' with one executive calling the band 'dead in the water.'

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

The name 'Silicon Valley' arose from the founding of Shockley Semiconductor Laboratory in Fairchild Semiconductor in 1956-57, founded near Stanford University in Palo Alto

When a Paris department store hesitated to sell Estée Lauder's perfume, she 'accidentally' broke a bottle, causing the smell to spread throughout the store and shoppers to start asking to buy the scent.

Mark Twain spent decades feuding with the US Postal Service, convinced its costs and regulations were bureaucratic overreach.

Experimental hantavirus vaccines and therapies, still under development, have long been funded by the US military.

Abraham Lincoln was almost assassinated weeks before his inauguration as he traveled from Illinois to DC through Baltimore in 1861; it took two independent claims for Lincoln to be convinced the threat was real

In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

In 1984, Operation Smash Hit intentionally crashed a 239-ton train into a nuclear waste canister at 100 miles per hour to prove the canister's safety, which remained completely intact and lost just 0.29 of its 100 pounds of pressure.

Electrical grids worldwide must double their power delivery capacity by 2050 to meet surging demand from AI and electric vehicles.

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

Louisiana's 'Cancer Alley' is infamous for having some of the highest industrial pollution, toxic air emissions, and cancer risks in the US.

Brandi Chastain, the star of the 1999 US victory over China in the 1999 Women's World Cup, was a last-second choice to take the penalty kick that sealed the victory.

How Amazon operates a 'flywheel' business model, a self-reinforcing cycle that drives continuous growth

Iran's Revolutionary Guard Corps is independent of Iran's regular army and is one of the most powerful and influential military-political organizations in the Middle East.