Whilst at the close of the American Civil War, President Lincoln argued for lenient and engaging treatment of the defeated South, during its prosecution he was passionately convinced that the preservation of the Union was essential and that this could only be ensured through war and victory.
He was initially frustrated, therefore, with the somewhat half-hearted attitude to the conflict that some of his senior military figures held. Some of the Unionist army knew some on the Confederate side reasonably well, and were not desperately enthusiastic.
Lincoln removed General Winfield Scott from the head of command, and turned to General George B McClellan, a 'young Napoleon' of 34 who he hoped would prove dynamic and effective in leading the troops.
However, the relationship between the men soured due to mistrust - partly because McClellan was a Democrat and believed that Lincoln would not grant him the resources which he would grant a Republican.
McClellan therefore stalled his attack on Richmond and repeatedly emphasised the forces against him and called for more resources. Lincoln lost patience with the exaggerations after it became clear that Confederate forces were moving North in some numbers.
His letter to McClellan on May 25 1862 dispensed with charm:
"The enemy is moving North in sufficient force to drive Banks before him—precisely in what force we can not tell. He is also threatening Leesburg, and Geary on the Mannassas Gap Railroad from both North and South—in precisely what force we can not tell.
"I think the movement is a general and a concerted—such as could not be if he was acting upon the purpose of a very desperate defense of Richmond.
"I think the time is near when you must either attack Richmond, or give up the job and come to the defense of Washington. Let me hear from you instantly."
McClellan's reply was conciliatory, promising the attack on Richmond was imminent. But a letter to his wife the same day makes it clear he was fuming:
"It is perfectly sickening to deal with such people & you may rest assured that I will lose as little time as possible in breaking off all connection with them".
McClellan held his post for five months, later unsuccessfully challenging Lincoln for the Presidency in 1864. Lincoln's blunt telegram brought $482,500 at the James S Copley Library sale at Sotheby's last week, showing the high value placed on this rare and valuable piece of Americana.
Collectors may be interested to know that another Lincoln autograph, promoting James H Carleton for a difficult mission, is currently available.