the French. The overconfidence and lack of preparation led to the disastrous defeat of the English, led by Edward II at the Battle of Bannockburn to the Scots, led by Robert the Bruce. The Spanish naval assault on England in 1588 suffered the defeat of the Spanish Armada. Similarly, English overconfidence the following year led to the disaster of the English Armada. 19th century The calamitous decision by Napoleon to invade Russia in 1812 led to the return of only 10,000 French soldiers when 610,000 had initially been sent out. Napoleon's repeated victories in Central Europe led him to believe that Russia would surrender after a few won battles, and made no plans for a sustained campaign or occupation in Russia. The first six weeks of the Franco-Prussian War saw French armies, convinced of their superiority following French victories in the Crimean War and the wars of Italian unification, enter a war with Prussia believing that their weapons and tactics would easily defeat the Prussians. However, the Prussians had better tactics and this led to catastrophic French defeats at Sedan and Metz. United States victories against Mexico and American Indians led Union forces to be overconfident going into the Civil War. Failing to update their tactics to match new technology, such as rifling of firearms and the use of the Minie ball as ammunition, they assumed that superior numbers would give them rapid victories, and ignored plans for an extended war until after repeated defeats. Confederate decisions made at and before their loss at the Battle of Gettysburg, after their outnumbered-five-to-two victory at the Battle of Chancellorsville and previous battles before then in the Eastern Theater of the American Civil War. Captain and Brevet Lt. Col. William J. Fetterman boasted during America's Indian Wars that, given "80 men," he would "ride through the Sioux nation". He had contempt for the Sioux's fighting ability and overconfidence in his own military prowess. In 1866, during Red Cloud's War, he and his army of exactly 80 men (including two volunteering civilians) were massacred to the last man by a combined force of Lakota, Northern Cheyenne, and Arapaho. It was possibly the worst army defeat on the Great Plains until eclipsed by the disaster at Little Bighorn ten years later. The 1876 Battle of the Little Bighorn, in which the Lakota and Northern Cheyenne annihilated five companies of the 7th Cavalry under Lt. Col.