More than 16 million Americans served in the U.S. Armed Forces during World War II. The 1970 Census identified 12.5 million World War II veterans living in the United States. In 2000, there were 5.7 million World War II veterans, and fewer than 500,000 in 2020. In 2023, the Census Bureau's American Community Survey estimated that just 91,008 veterans of that war remained.

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World War II began with the German invasion of Poland on September 1, 1939. Japan's invasion of French Indochina made the conflict a global war in 1940. When hostilities began, the United States was initially committed to remaining neutral but it allowed other nations to purchase war materiel and lent Great Britain naval ships in exchange for 99-year base leases. In the Pacific, the United States increasingly imposed trade restrictions, embargoes, and economic sanctions on Japan while offering purchase credit and supplies to China.

Fearing American interference in their campaign of Asian expansion and resources acquisition, Japan launched a surprise attack on Pearl Harbor, Hawaii, hoping to cripple the U.S. Navy's Pacific Fleet. Despite sinking or damaging 19 U.S. Navy ships (including eight battleships) and destroying 188 aircraft, the attack failed to destroy repair and oil infrastructure or damage any of the fleet's aircraft carriers. Following the attack, the United States declared war on Japan on December 8 and Germany on December 11, 1941.

After the attack on Pearl Harbor brought the United States into the war, the Allies (the United States, the United Kingdom, and the Soviet Union) agreed on a strategy to defeat the Axis (Germany, Japan, and Italy). The majority of resources would focus on defeating Germany and Italy first, while halting Japanese expansion.

By 1943, the Axis had suffered defeats in North Africa, Eastern Europe, and Italy. The June 1944 D-Day invasion opened yet another front in Western Europe, which forced Germany into a gradual retreat. By April 1945, the Allies had encircled the remaining Nazi force near Berlin. Germany officially surrendered on May 8, 1945.  Celebrants around the world cheered Victory in Europe (VE) Day. However, as Harry S. Truman, who became President after the death of Franklin D. Roosevelt in April 1945, cautioned, “Much remains to be done. The victory won in the West must now be won in the East.”

In the Pacific, the Allies halted the Japanese advance in June 1942 at the Battle of Midway. They then built on this momentum through a series of hard-fought island battles that brought them ever closer to the Japanese homeland. So as Europe began its recovery, the war raged on in the Pacific and the Allies shifted their focus and resources there.

As American bombers decimated Japanese cities, American troops captured the island of Okinawa in June 1945. In July, General Douglas MacArthur liberated the Philippines. That only left the Japanese mainland left to conquer in what promised to be a long and bloody battle. Instead of the invasion, the United States dropped the first atomic bomb on Hiroshima on August 6. Two days later, the Soviet Union declared war on Japan and invaded Manchuria. The United States dropped a second atomic bomb on Nagasaki on August 9. The next day, Japan agreed to accept the Allies' terms of surrender if the rule of Emperor Hirohito could be preserved. On August 15, Japanese citizens heard the voice of Emperor Hirohito for the first time when he announced Japan's surrender during a radio broadcast. The deadliest war in human history came to an end with the celebration of VJ Day. Japan signed the formal Instrument of Surrender aboard the USS Missouri (BB-63) anchored in Tokyo Bay on September 2, 1945.

You can learn more about World War II using U.S. Census Bureau data and records. For example:

• The September 27, 1940, signing of the Tripartite Pact formally allied the "Axis Powers" of Germany, Italy, and Japan. In that year, the 1940 Census reported that 1,237,772 people of German ancestry lived in the United States. The nation's population also included 126,947 Japanese (47,305 of whom were foreign-born), and 1,623,580 Italians. In total, the United States' foreign-born population was 11,419,138, with the largest number living in New York (2,853,530), Pennsylvania (973,260), and Illinois (969,373).
• Between 1940 and 1941, the United States halted nearly all exports of critical resources like oil and metal from the United States to Japan in response to Japan's military expansion in Asia and its alliance with Germany and Italy. In the decades after the war, trade resumed. In 1985, Census Bureau data showed that the United States exported more than $22.6 billion of goods to Japan and imported nearly $68.8 billion of products from Japan. In 2000, exports were greater than $64.9 billion, while imports reached nearly $146.5 billion. In 2024, the United States exported almost $79.0 billion of goods like liquified natural gas, pharmaceutical preparations, meat and poultry, industrial machines, medicines & medical equipment, civilian aircraft, engines and parts, and corn to Japan and imported nearly $148.4 billion of goods, such as autos, auto parts, and electronics.
• Between 1941 and 1945, thousands of American manufacturers mobilized their workforces and retooled factories to support the war effort. Oldsmobile employees in Lansing, MI, built Howitzers and millions of artillery shells; Ford Motor Company employees built B-24 bombers at the company’s Willow Run complex near Ypsilanti, MI; watch workers in Waltham, MA, made rugged wristwatches that survived severe conditions on the land, in the sea, and in the air; and brass manufacturers in and around Waterbury, CT, produced cartridge cases, mortar shells, bullets, and bomb components. Today, thousands of Americans work in industries supplying the U.S. Armed Forces. For example, in 2023, the Census Bureau's County Business Patterns series found that 62 Military Armored Vehicle, Tank, and Tank Component Manufacturing (NAICS 336992) establishments employed 11,831 employees; 172 Small Arms Ammunition Manufacturing (NAICS 332992) establishments employed 13,789; and 523 Small Arms, Ordinance, and Ordinance Accessories Manufacturing (NAICS 332994) establishments employed 25,999 people during the pay period that included March 12, 2023.
• The 1890 Census was the first to include "Japanese" as a response to the race category and 2,039 people identified as such. Most Japanese lived in California (1,147) and Washington (360). The Census Bureau conducted the 1940 Census the year before the United States declared war on Japan on December 8, 1941, and counted 126,947 Japanese (79,642 native and 47,305 foreign born). California (93,717) and Washington (14,565) continued to be home to the largest Japanese populations. In 1950, the Japanese American population numbered 141,768. California still had the largest Japanese American population with 84,956. In 2023, data from the Census Bureau's American Community Survey estimated there were 725,773 people in the United States who identified as Japanese alone. California (238,913) and Hawaii (161,089) had the largest number of people identifying as Japanese alone in the United States.
• Japanese Americans played critical roles in support of the American war effort and more than 33,000 served in the U.S. military. Many of these soldiers served in the 442nd Infantry Regiment, 100th Infantry Battalion which was composed almost entirely of second-generation American soldiers of Japanese ancestry (Nisei). Between 1944 and 1946, the 442nd earned more than 4,000 Purple Hearts, 4,000 Bronze Stars, and seven Presidential Unit Citations, and 21 members were awarded the Medal of Honor during their service in Italy, southern France, and Germany. Medal of Honor recipients included:
  • Sadao S. Munemori, Los Angeles, California. Private First Class Munemori was the first Japanese American awarded the Medal of Honor for his actions on April 5, 1945. During an attack on German positions in the Apennines Mountains in Northern Italy, Munemori silenced two machine gun nests. After seeking cover in a shell crater, he dove atop a grenade to absorb the blast, sacrificing his own life to save the lives of two nearby comrades.
  • Joe Hayashi, Los Angeles, California. Then-Private Hayashi earned the Medal of Honor for extraordinary heroism in battle near Tendola, Italy. On April 20, 1945, he braved enemy fire to direct mortar rounds on enemy positions. Two days later, he single-handedly destroyed three enemy machine gun positions before being killed while pursuing the enemy.
  • Daniel K. Inouye, Honolulu, Hawaii. In fighting near San Terenzo, Italy, then-Second Lieutenant Inouye led his platoon against enemy positions, capturing or destroying German mortar, artillery, and machine gun positions despite being wounded by a sniper and having his right arm shattered by a grenade blast. The arm was eventually amputated. For this, he received the Bronze Star and Distinguished Service Cross. This was upgraded to the Medal of Honor in June 2000. After the war, he was elected to Hawaii's territorial House of Representatives and Senate. He was elected to the House of Representatives following Hawaiian statehood in 1959 and became a U.S. senator in 1962. He served as Hawaii's senator until his death in 2012.
  • Kiyoshi K. Muranaga, Los Angeles, California. In 1942 Muranaga and his family were interned at the Granada War Relocation Center, near Granada, Colorado. He joined the U.S. Army in May 1943. On June 26, 1944, he manned his squad's mortar alone in an open position in an attempt to destroy a German self-propelled 88mm gun. A round from the German gun killed Private First Class Muranaga as his mortar fire forced the enemy gun crew to abandon their position.
  • Allan M. Ohata, Honolulu, Hawaii. On November 29-30, 1943, Staff Sargeant Ohata and four others fought off multiple attacks near Cerasuolo, Italy, killing dozens of heavily-armed German soldiers. He was awarded the Medal of Honor on June 21, 2000, nearly 23 years after his death.
  • James K. Okubo, Anacortes, Washington. In 1942, Okubo and his family were interned at the Tule Lake War Relocation Center near Newell, California, and later the Heart Mountain Relocation Center near Ralston, Wyoming. He joined the U.S. Army in May 1943. During fighting in the French Vosges Mountains on October 28-29, 1944, Technician Fifth Grade Okubo exposed himself to enemy fire to treat 25 wounded comrades. Days later, he dodged machine gun fire to save the life of a wounded soldier who would have died in his burning vehicle had Okubo not come to his rescue. The Okubo Barracks at Fort Sam Houston, Texas, and Okubo Family Health Clinic at Joint Base Lewis-McChord, Washington, are named in honor of the 442nd Infantry veteran.
• Approximately 16 million Americans served in the U.S. Armed Forces during World War II. Among them:
  • Eight presidents of the United States: Dwight D. Eisenhower, John F. Kennedy, Lyndon B. Johnson, Richard Nixon, Gerald Ford, Ronald Reagan, George H.W. Bush, and Jimmy Carter.
  • American military leaders: Creighton Abrams, George Marshall, Douglas MacArthur, Omar Bradley, Mark Clark, George S. Patton, Chester W. Nimitz, Raymond Spruance, and Carl Spaatz.
  • Other notable veterans of World War II include Medal of Honor recipient and movie star Audie Murphy; Olympian Louis Zamperini; baseball players Ted Williams, Joe DiMaggio, Yogi Berra, and Jackie Robinson; Civil Rights activist Medgar Evers; movies stars Clark Gable and Jimmy Stewart; astronauts Alan Shepard and Deke Slayton; retail entrepreneur Sam Walton; and big band conductor Glenn Miller.

• Emperor Hirohito announced Japan's surrender in a radio address on August 15, 1945. The surrender was formalized when representatives of the Japanese government and armed forces signed the Japanese Instrument of Surrender aboard the USS Missouri (BB-63) on September 2, 1945. The Brooklyn Navy Yard built the Missouri and more than 160 other ships between 1801 and 1966. In addition to the Missouri, the shipyard also built historic ships like the Civil War ironclad Monitor; battleship Arizona (BB-39); and the aircraft carriers Saratoga (CV-60), Independence (CVA-62), and Constellation (CVA-64). Although the United States still operates shipyards for maintenance, repair, and modernization, shipbuilding is performed by contractors. In 2022, there were 397 U.S. employer firms (compnies with at least one paid employee) in the Ship Building and Repairing sector (NAICS 336611). That same year, these firms had sales, value of shipments, or revenue of more than $31.4 billion and employed 103,457 people.

On August 25, 1864, Confederate soldier Jacob W. Cobb, Jr. captured future Superintendent of the Census Francis Amasa Walker during the Civil War's Second Battle of Ream's Station.

Released during an October 1864 prisoner exchange, Walker returned to his family's home in North Brookfield, MA.

Walker was working at a Springfield, MA, newspaper when President Ulysses Grant appointed him to supervise the 1870 Census. A decade later, President Rutherford B. Hayes asked Walker to oversee the 1880 Census.

Learn more about Walker in Captured! The Civil War Experience of Superintendent of the Census Francis Amasa Walker.