World War II: Operation Carpetbagger, involving the dropping of arms and supplies to resistance fighters in Europe, begins.

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 Carpetbagger was a World War II operation to provide aerial supply of weapons and other matériel to resistance fighters in France, Italy and the Low Countries by the U.S. Army Air Forces that began on 4 January 1944.

January 4 is the fourth day of the year in the Gregorian calendar; 361 days remain until the end of the year.