Among the many notable things he is known for, Abraham Lincoln was also gifted at one-liner responses. Frustrated with General McClellan's lack of initiative on the battlefield, Lincoln sent the General note saying, "If you don’t want to use the army I should like to borrow it for a while."
Below is a letter Lincoln wrote to General Joseph Hooker 151 years ago, who succeeded General Burnside who succeeded McClellan as the commander of the Army of the Potomac. Lincoln was frustrated, to quote Anthony Bergen, "by the fact that 'Fighting Joe' wasn't fighting so hard."
The full text of the letter is below. I have italicized Lincoln's "zinger" in the body of the letter.
Washington, January 26, 1863
I have placed you at the head of the Army of the Potomac. Of course I have done this upon what appear to me to be sufficient reasons. And yet I think it best for you to know that there are some things in regard to which, I am not quite satisfied with you. I believe you to be a brave and a skillful soldier, which, of course, I like. I also believe you do not mix politics with your profession, in which you are right. You have confidence in yourself, which is a valuable, if not an indispensable quality. You are ambitious, which, within reasonable bounds, does good rather than harm. But I think that during Gen. Burnside's command of the Army, you have taken counsel of your ambition, and thwarted him as much as you could, in which you did a great wrong to the country, and to a most meritorious and honorable brother officer. I have heard, in such way as to believe it, of your recently saying that both the Army and the Government needed a Dictator. Of course it was not for this, but in spite of it, that I have given you the command. Only those generals who gain successes, can set up dictators. What I now ask of you is military success, and I will risk the dictatorship. The government will support you to utmost of it's ability, which is neither more nor less than it has done and will do for all commanders. I much fear that the spirit which you have aided to infuse into the Army, of criticising their Commander, and withholding confidence from him, will now turn upon you. I shall assist you as far as I can, to put it down. Neither you, nor Napoleon, if he were alive again, could get any good out of an army, while such a spirit prevails in it.
And now, beware of rashness. Beware of rashness, but with energy, and sleepless vigilance, go forward and give us victories.
Yours very truly
Source: Dead Presidents