World War II was a global conflict that lasted from 1939 to 1945, involving most of the world's nations. It was marked by significant events such as the Battle of Britain, the Holocaust, and the use of atomic bombs on Hiroshima and Nagasaki. The war resulted in an estimated 70-85 million fatalities, making it the deadliest conflict in human history. The aftermath of World War II led to the establishment of the United Nations in 1945, aimed at fostering international cooperation and preventing future conflicts. The war also resulted in the division of Europe and the beginning of the Cold War, shaping global politics for decades to come.