September 15 in Military History

British forces under General William Howe landed at Kip's Bay on Manhattan Island and routed the defending Connecticut militia. Washington's Continental Army evacuated most of its troops to Harlem Heights, but the loss of New York City was a devastating blow. The British would hold the city for the remainder of the war, using it as their primary base of operations.

Confederate forces under Stonewall Jackson captured the US Army garrison at Harpers Ferry, Virginia, taking 12,500 Union soldiers prisoner in the largest US military surrender of the nineteenth century. The captured troops were paroled and released, but 13,000 small arms, 73 artillery pieces, and substantial stores were sent south. Jackson then marched to rejoin Lee at Sharpsburg, arriving in time for the Battle of Antietam.

A Japanese naval squadron under Admiral Ito Sukeyuki decisively defeated the Chinese Beiyang Fleet at the mouth of the Yalu River during the First Sino-Japanese War. The engagement was the largest naval battle since Trafalgar and the first fought between steam-powered steel warships. Japanese gunnery, training, and rapid-fire guns overcame the Chinese heavy battleships, establishing Japanese control of the Yellow Sea and enabling the advance on Port Arthur and Weihaiwei.

German, French, and British forces clashed along the Aisne River as the German retreat from the Marne halted at prepared positions on the heights north of the river. The five-day engagement produced the first true trench stalemate of the Western Front. Both sides began constructing the continuous trench line that would extend from the Channel to the Swiss border and define the war for three and a half years.

British Mark I tanks went into action for the first time at the Battle of Flers-Courcelette during the Somme offensive. Of the 49 tanks committed, only 32 reached the start line, and many broke down or became stuck in the mud. Despite their mechanical unreliability, the tanks terrified German defenders and advanced up to a mile in places, demonstrating the potential of armored warfare.

The Nazi regime enacted the Nuremberg Laws at the annual party rally, stripping German Jews of their citizenship and prohibiting marriage or sexual relations between Jews and non-Jews. The laws provided the pseudo-legal framework for the escalating persecution that would culminate in the Holocaust and influenced military policies regarding who could serve in the Wehrmacht.

The Royal Air Force inflicted devastating losses on the Luftwaffe over London, shooting down 56 German aircraft while losing 29 of their own. The scale of the RAF's victory demonstrated that Fighter Command had not been broken and that German air superiority, the prerequisite for invasion, was unachievable. Two days later, Hitler postponed Operation Sea Lion indefinitely.

US forces executed two simultaneous amphibious landings in the Pacific: MacArthur's Southwest Pacific Area forces landed on Morotai in the Dutch East Indies, and Nimitz's Central Pacific forces under Halsey landed at Peleliu in the Palau Islands. Morotai was lightly defended and became an airfield base for the liberation of the Philippines. Peleliu became one of the costliest battles of the Pacific War.

General MacArthur launched Operation Chromite, an audacious amphibious assault at Inchon, 150 miles behind North Korean lines. The landing achieved complete tactical surprise and transformed the Korean War overnight.

The collapse of Lehman Brothers triggered the global financial crisis that would eventually lead to significant cuts in defense spending worldwide. The resulting sequestration and austerity measures forced the U.S. military to reduce its force structure, delay modernization programs, and scale back training, effects that military leaders warned would take years to reverse.