World War II: Launch of Operation Ratweek, complicating German retreat.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

Operation Ratweek was a series of coordinated attacks on the Axis forces' communication lines in the Balkans during World War II. Launched on 1 September 1944. the attack was led by the combined operations units of the Yugoslav Partisans, Land Forces Adriatic, the heavy bombers of the U.S. 15th Air Force and the light and medium bombers of the Balkan Air Force.

September 1 is the 244th day of the year in the Gregorian calendar; 121 days remain until the end of the year.