Germany invades Poland, leading Great Britain and France to declare war against Germany.

In the first large scale “bombing war,” Britain’s Royal Air Force (RAF) bombs the Ruhr area of Germany, specifically civilian industrial targets that are known to aid the German war effort.

As U.S. participation in World War II looks more likely, Secretary of War Henry Stimson establishes the Army Air Forces, a reorganization of the previous Air Corps that enables increased autonomy within the U.S. War Department.

A British study shows that RAF bombing is typically inaccurate, with only 20% of aircrews navigating to within five miles of their assigned targets. This report leads to a major shift in Britain’s bombing strategy, shifting away from military targets and towards the main residential and industrial centers in Germany.

In a surprise early morning attack, Japan bombs Pearl Harbor and declares war on the U.S. and the U.K. Four days later, Germany and Italy will declare war on the U.S. as well.

Winston Churchill and U.S. President Franklin Roosevelt meet at the White House for the Washington/Arcadia Conference and agree to build up American air power in England.

Allied forces activate the VIII Bomber Command, the first operational element of the 8th Air Force, to coordinate and lead the air attack on Germany. General “Hap” Arnold, commanding general of the AAF, appoints Ira Eaker to lead this bombardment force. “The Mighty 8th” will dominate the American strategic air war against Germany, though it will become a part of the larger U.S. Strategic Air forces in a reorganization early in 1944.

British Prime Minister Winston Churchill appoints Air Marshal Arthur Harris to Commander in Chief of the Bomber Command in order to carry out the new strategy of the RAF.

272 British bombers of the RAF attack Hamburg at night, signifying the largest raid yet on a single target.

In response to Allied bombing that the Nazi’s call “terror raids,” the German air force — the Luftwaffe — bombs Exeter, England, in part of its “Baedeker Blitz.”

898 RAF bombers attack the German city of Cologne in Operation Millennium. This new “bomber stream” tactic will become the standard for air force operations until 1944.

In the first American mission against a European target, 12 U.S. Army Air Force (USAAF) B-24 bomber planes attack the oil refineries at Ploesti, Romania. Ploesti will continue to be under attack throughout the war as a Nazi supplier of equipment and oil.

The first B-17 “Flying Fortress” arrives in Great Britain, earning its name from its heavy armament and ability to return from missions despite sustaining extensive damage. American airmen hoped that such aircraft could get through German defenses and hit their targets without fighter escort.

USAAF pilots collaborate with the RAF on a bombing mission targeting German airfields in Holland.

General Ira Eaker flies with the first B-17 Flying Fortress strike on occupied France. Of the 18 Flying Fortress aircraft deployed, only two will be damaged, and all will return after the successful bombing of railroad yards in Rouen-Sotteville.

Brigadier General Curtis LeMay brings new “combat box” tactic to a bombing run over St. Nazaire, France. Rather than practice evasive maneuvering, LeMay’s group flies in staggered formation that allows them to defend themselves without escort planes. Allies lose only four bombers to the enemy and a greater percentage of bombs ultimately hits their targets.

More than 1,200 aircraft and 27,000 men transfer to operations in the Mediterranean. Included in this transfer is the popular Brigadier General James “Jimmy” Doolittle, who will lead the 12th Air Force for Operation TORCH, and later the 15th Air Force in the Mediterranean, fighting the Axis forces in North Africa and Italy.

The 8th Air Force attacks St. Nazaire and loses seven bombers to a new German anti-aircraft tactic called “predicted barrage” in which Nazi ground gunners fire a lethal box of explosives into the air, hitting bombers who attempt to maneuver through the enemy airspace.

As the Casablanca Conference, Roosevelt and Churchill confirm their goal of securing the Axis nations’ surrender. To achieve this, they agree upon a combined bomber offensive: the British will strike at night, while the Americans will bomb by daylight.

In their first attack on German soil, 91 B-17s and B-24s of the 8th Air Force target submarine yards in Wilhelmshaven, Germany. The daytime operation is a success, as Wilhelmshaven sustains losses to many important industrial plants and the Nazis lose 22 planes to only three USAAF bombers.

The RAF attacks Berlin for the first time using Mosquito planes, unarmed bombers known for their speed. The RAF will continue to use Mosquito aircraft extensively in their strategic night raids.

American P-51 Mustang fighter planes fly their first mission over Europe. The Mustang was designed for use as a bomber and reconnaissance plane, but evolved into an escort aircraft as the war progressed. The Mustang planes were heralded as an example of the Allied forces’ technological superiority in the air war.

In extensive air-to-air fighting with German planes over Bremen, the 8th Air Force loses 16 unescorted bombers due to heavy anti-aircraft artillery but are able to damage more than half of Bremen's Focke-Wulf airline production factories.

The Pointblank directive begins. A combined British and American offensive, Pointblank consists of a constant onslaught on German industry through British raids at night and American raids during the day.

Hitler makes the V2 Missile program a top priority. The V2 will be the world’s first long-range ballistic missile, and is created to help defend German forces from the Allies’ advanced air force technology.

Over the course of ten days, the RAF and the 8th Air Force devastate Hamburg with heavy bombing. The attack, named “Operation Gomorrah,” will leave more than 13 square miles destroyed and kill more civilians than the Germans’ entire Blitz over Great Britain in April 1942.

Allied bombers suffer heavy losses in an attack over a heavily fortified oil refinery at Ploetsi, Romania. The attack results in 446 airmen killed or missing, 54 wounded and 79 captured as POWs. Although more than 175 B-24s participate in the operation, only 33 will be in working order after the raid.

Although initially damaged in the raid, the oil refinery will be quickly repaired and returned to operation.

Black Thursday - Nearly 600 crew members are lost in this long-range Allied bombing raid that targets a heavily defended ball-bearing factory in Schweinfurt, Germany. 60 B-17 Flying Fortresses are lost under heavy German antiaircraft fire.

Escorted by fighter planes for the first time both to and from their targets, 710 bombers take part in the largest daylight raid thus far over Kiel, Germany. The attack results in the loss of five Allied bombers and 15 Nazi fighter planes.

Lt. General Ira Eaker is removed from his command with the 8th Air Force and transferred to command air operations in the Mediterranean theater. General Spaatz takes command of the United States Strategic Air Forces in Europe (USSTAF). Lt. General James Doolittle is placed in command of the 8th Air Force.

James Doolittle will send Mustang fighters to defend bomber groups by going on the offense. The Mustangs fly ahead of bombers to attack the Luftwaffe, as well as hit them on the ground. The Mustang's success rate was reputed to equal 19 kills for every one Mustang lost. The P-51 is credited with the destruction of 4,950 German planes, more than any other Allied fighter plane.

As part of Operation Argument and what would become known as “Big Week,” the Allies wage a six-day air campaign over Western Europe that targets aircraft manufacturing plants in an attempt to cripple Germany’s aircraft industry.

The Allies bomb Berlin with 12,000 airmen, dropping thousands of tons of explosives. Heavy losses are sustained on both sides; in one nighttime raid on the 24th, RAF forces lose 72 aircraft. Despite the losses, the Allies are able to replace their forces while the Germans are not.

For several days, British and American forces bomb transportation hubs, oil refineries, bridges and roads in occupied Europe, including dropping 81,110 tons of bombs on the French railway system. This air support, known as Operation Cover, will prove vital to Allied success on D-Day.

D-Day: after a nighttime air assault, over 160,000 Allied troops land along the Normandy coast. Operation Overlord, the maneuver to land troops on the beach, is the largest amphibious invasion of all time. D-Day marks the first day of the Anglo-American invasion of Europe.

Adolf Hitler issues an order that all shot down Allied airmen are to be “shot or lynched on capture.”

Sustaining unprecedented damage, the Luftwaffe will lose an average of 300 aircraft per week.

Allied troops liberate Paris. The Nazis retreat across the Seine.

Germany’s V2 missile technology is finalized and the first V2 is launched at Paris and London. The rocket V2 was the first long-range combat-ballistic missile ever created and the first missile to achieve sub-orbital spaceflight. Over the next few months, over 3,000 V2s are fired at various Allied locations, causing over 7,250 military personnel and civilian casualties.

As part of a strategy to discourage Nazi morale, the RAF bombs Darmstadt, Germany and the resulting firestorm kills more than 10,000 people. The Nazis condemn this raid as an example of Allied “terror bombing.”

The Battle of the Bulge begins as a desperate attempt by the Nazis to defeat the approaching Allied army.

After being initially hampered by bad weather, the 8th Air Force provides desperately needed air support to Allied troops engaged in the Battle of the Bulge. The bombers drop more tonnage than any other single day of the war, helping to turn the course of the battle.

The Germans usher in the New Year by launching a pre-dawn raid against Allied airfields. More than 450 Allied planes are destroyed, but the attack proves more costly to the Germans, who lose 237 pilots, 59 of whom are commanders.

German forces are pushed back and defeated, ending the Battle of the Bulge. In what was the bloodiest battle the Americans faced in the war, 19,000 troops were killed in the month-long fight. The Nazis, however, sustained an estimated 100,000 casualties.

When Carl Spaatz directs General Jimmy Doolittle to bomb targets in the center of Berlin, Doolittle warns that this attack will “violate the basic American principle of precision bombing of targets of strictly military significance.”

More than 900 bombers and over 550 fighter escorts — the largest force ever sent against a single city to date — begin the bombing of Berlin. The American forces target German government centers and railway stations filled with civilian refugees.

Churchill, Stalin and Roosevelt meet at Yalta to plan the final defeat of the Nazis. The leaders will also establish a guideline for post-war reorganization and re-establishment of European countries.

800 bombers drop 4,000 tons of explosives and incendiaries on Dresden, Germany targeting the train yard and passenger station. The combination sets off a firestorm that will kill more than 35,000 people.

The RAF and 8th Air Force bombers begin a two-day attack on lightly or non-defended transportation targets as part of Operation Clarion.

General Eaker had warned General Spaatz that the operation “would absolutely convince the Germans that we are the barbarians they say we are, for it would be perfectly obvious to them that this is primarily a large-scale attack on civilians as, in fact, it of course will be. Of all the people killed in this attack over 95% of them can be expected to be civilians.”

1,200 U.S. bombers strike Berlin in an attempt to disrupt the communications of the already impaired Nazi army. By the end of the next month, there will be a total of 363 air raids on Berlin with casualty estimate around 20,000.

Allied aircraft accidentally bomb Basel and Zurich, Switzerland. In response to bad press and a diplomatic crisis sparked by this mistake, General Spaatz issues a directive that only military objectives are to be attacked.

U.S. forces cross the Rhine River in Germany.

1,329 Allied bombers and 700 long-range fighters meet heavy resistance by German jets and fighters over Berlin. The 8th Air Force loses six Mustangs and 13 bombers while the Lutwaffe, using the new jet powered Me 262s and air-to-air rockets, lose only two planes, despite being outnumbered 32 to 1.

Germany sends out 120 student pilots to face 1,000 American bombers in a suicidal operation. In a plan approved by Hitler, pilots are ordered to ram their planes into the American fleet and attempt to parachute to safety. Only a few German attackers will hit the bombers, and 3/4 of the Luftwaffe fighter pilots will be killed in action.

In what will become known as the “day of the great jet massacre,” Allied aircraft shoot down half of the German Messerschmitt Me 262 jet fighter planes. The loss proves fatal to the Luftwaffe and the defense of Berlin is abandoned.

U.S. President Franklin Roosevelt dies, leaving Vice President Harry Truman in charge.

Carl Spaatz declares that the Strategic Air War has been “brought to a close” and “won with a decisiveness becoming increasingly evident as our armies overrun Germany.”

The 8th Air Force bombs train yards in Dresden, Germany, killing 500 civilians.

The Luftwaffe shoots down five Allied bombers in a mission over Aussig, Czechoslovakia. These will be the last planes lost to the Luftwaffe.

American and Soviet Armies meet at the Elbe River.

With Soviet troops fewer than 500 meters away, Adolf Hitler commits suicide in a bunker by a combination of cyanide poisoning and a gunshot wound to the head.

The German Army surrenders to the Allied expeditionary force in Reims.

V-E Day — Europeans flock to the streets in celebration of the victory over the Nazis one day after the German Army surrendered to the Allied expeditionary force in Reims.

The 8th Air Force begins to return to the United States, but soon redeploys to the Pacific Theater where they will be reassigned to Okinawa under Lieutenant General Jimmy Doolittle, with the mission to organize and train new bomber groups for combat against Japan.

The Enola Gay, part of the USAAF's 509th Composite Group, drops the Atomic Bomb on Hiroshima, Japan.

V-J Day — Japan surrenders to the Allies, officially ending World War II. Emperor Hirohito announces the unconditional surrender over Japanese radio, accepting the terms of the Potsdam Declaration.

The Air Force becomes its own arm of the American Military, releasing its tie to the Army.