Book excerpt: On the crucial third day of the decisive Battle of Gettysburg, a newly-appointed brigadier general, age 23, commanded a full brigade of Michigan cavalrymen during his first major battle ? George Armstrong Custer. He played a key role in saving the day in the Army of the Potomac's rear by leading his four cavalry regiments to victory. This book has emphasized the importance of the decisive clash at the East Cavalry Field on July 3, 1863 by presenting Custer's official report?long considered ""lost"" and often ignored?about the most important cavalry action during the largest and most decisive battle ever fought on the North American continent. Most of all, this is an important story about the Union cavalry's vital contributions to decisive victory on the final day of the most climactic showdown of the Civil War at Gettysburg.