October 18
Politics, United States
Vice Admiral William Halsey replaces Vice Admiral Robert Ghormley as South Pacific Area commander.

October 22
Air War, Italy
Britain launches a series of raids on the industrial areas around Turin, Milan, and Genoa.

October 23
Africa, Egypt
The Battle of El Alamein begins. General Bernard Montgomery's carefully-prepared attack by 195,000 Allied troops against 104,000 Axis men begins with an enormous artillery bombardment and numerous deception measures. Massive mine-clearance operations enable Allied armor formations to push forward and leave the infantry to widen the gaps. Field Marshal Erwin Rommel is in Germany, but immediately returns after the temporary commander, General Georg Stumme, dies suddenly. First reports confirm that the Allies have made an excellent start, although Axis resistance is fierce.

October 26
Sea War, Pacific
At the Battle of Santa Cruz, Japanese carriers approach Guadalcanal and fatally damage the US carrier Hornet (leaving the US Pacific Fleet with one carrier). The Japanese cruiser Yura is sunk and the carrier Shokaku rendered ineffective by aircraft strikes.

A Japanese bomber in action against US warships during the Battle of Santa Cruz