[War] does not consist of a single instantaneous blow.... much more strength of will is required to make an important decision in strategy than in tactics.The defensive, according to our conception, is nothing but the stronger form of combat.Every assailant in advancing diminishes his military strength by the advance ... This loss in the advance is increased if the enemy has not been beaten, but withdraws of his own accord with his forces intact...
The army in retreat has the means of collecting provisions everywhere, and he marches towards them, whilst the pursuer must have everything brought after him, which, as long as he is in motion, even with the shortest lines of communication, is difficult, and on that account begets scarcity from the very first.
The greater the masses are, the more severe are the exertions demanded from each individual for the daily duties required strategically and tactically. A hundred thousand men who have to march to and from the point of assembly every day, halted at one time, and then set in movement again, now called to arms, then cooking or receiving their rations—a hundred thousand who must not go into their bivouac until the necessary reports are delivered in from all quarters—these men, as a rule, require for all these exertions connected with the actual march, twice as much time as 50,000 would require, but there are only twenty-four hours in the day for both
For those supposing, judging his actions, that Lincoln knew Clausewitz, a few points Lincoln may have overlooked: