never sent, or signed

Called "the most important letter never sent," on July 14, 1863, ten days after the last battle at Gettysburg, President Lincoln put pen to paper and just evicerated his General of the Union Army, General George Meade. General Meade looked like yertle the turtle and he had allowed General Lee and the Confederate Army to escape back across the Potomac to Virginia. Now, complained Lincoln, the Civil War was going to go on forever! 

"As it is, the war will be prolonged indefinitely!"

Nevermind, that the Union Army and General Meade had just won the most important, and the bloodiest, battle to date—more than 51,000 casualties combined, at Gettysburg.

Meade failed to pursue Lee, the confederates escaped across the Potomac, and the war continued nearly two more years before ending with Lee's surrender at Appomattox Court House in Virginia on April 9, 1865.

But Lincoln famously thought over the harsh letter and never delivered it, leaving it sealed in an envelope marked “To Gen. Meade, never sent, or signed.”

Image 1 of Abraham Lincoln papers: Series 1. General Correspondence. 1833-1916: Abraham Lincoln to George G. Meade, Tuesday, July 14, 1863 (Meade's failure to pursue Lee) | Library of Congress 

Lincoln letter on Gettysburg found at U.S. archives