Thayer strongly admired Napoleon and took inspiration from his Ecole Polytechnique. He broke decisively with the standard university curriculum that placed heavy emphasis on Greek and Latin. Instead he built West Point as a true school of engineering, an outstanding one that set a standard for other universities to match. Thayer’s protégé Dennis Mahan was also an ardent follower of the French. In teaching principles of military leadership, Mahan instructed his cadets to seize the offensive, to maneuver and advance with speed. In the classroom he was as formidable as a thirty-six-pounder. Years after leading his march to the sea, General Sherman still shuddered to think of the times when Mahan had caught him unprepared.

It is not true the Army shut down after Appomattox. It only seemed that way.

The Mexican War gave many West Pointers their first opportunities for wartime command, and Gen. Winfield Scott, who led the drive on Mexico City, regarded their contributions as decisive: “I give as my fixed opinion, that but for our graduated cadets, the war between the United States and Mexico might, and probably would, have lasted some four or five years, with, in its first half, more defeats than victories falling to our share.”

The shapers of the next war also received their commissions at the Point: Robert E. Lee, Stonewall Jackson, George McClellan, Grant, Sherman, Beauregard, and many others. Most of them had come up under Mahan, a man who never saw a battle but whose teachings and writings defined the manner in which much of the Civil War was fought. Mahan had praised the “dashing bold hussar,” and Lincoln went on to measure his generals against this standard. He had to, for none was more dashing and bold than Lee.

It is not true that in the wake of Appomattox the United States Army went out of existence. It only seemed that way. During the war 2,666,999 men served at one time or another, and close to 1,000,000 stood ready for duty at its close. Within six months some 800,000 of them were back home. In 1866 Congress set the strength of the peacetime Army at 54,302 officers and men (which still was three times the authorized strength in 1860), and in 1870 it cut the number to 30,000. During the next three decades the true strength was generally lower; America had a permanent Army less than half the size of Belgium’s.

This force stayed active in Indian wars, but for most career soldiers the dominant theme was boredom. On isolated posts scattered across the West, life was a routine of inspections and dusty marching in close-order drill to the bark of a sergeant. The sun was merciless in summer. New faces were rare. Many of the men took to drink.

With no foreign foe at hand, and the Indians retreating to their reservations, there was reason enough to wonder whether the nation even needed an army. The situation at sea was similar. The U.S. Navy had not spent the century collecting barnacles; it showed the flag in overseas ports, and Commodore Perry opened Japan to the outside world. Then, to fight the Confederacy, the Union built a fleet that was mighty indeed—626 vessels, nine times the prewar total, among them 65 powerful ironclads.

But after that war our strength at sea declined as precipitously as our power on land. Ironclads were laid up and left to rot, and converted merchant ships returned to civilian ownership. The Navy retreated from steam power to sail, which was much cheaper. Indeed, when a ship carried both sails and a steam engine, the captain had orders not to use the latter unless he could justify his reason for doing so. By 1880 we had only a few ships capable of regular cruising, and virtually none in a condition to fight.

America was, in effect, at the mercy of any naval power that cared to fire a shot across our bow. Such a situation was insupportable, and the 188Os saw the beginnings of change, as three steel cruisers joined the fleet. In 1890 Congress voted funds for three new battleships, and British observers declared the resulting vessels a match for their country’s best.

That same year brought another milestone in the history of our peacetime military; Little, Brown & Company published The Influence of Sea Power on History . The book sparked the rise of our modern Navy. It came at a time when our burgeoning steel industry gave us the means to build a powerful fleet and growing overseas interests gave us reason to think we could use it. The historian Barbara Tuchman has described it as one of the most influential books of the nineteenth century, standing on a par with Darwin’s Origin of Species and Marx’s Das Kapital .

The book’s author was Alfred Thayer Mahan, president of the Naval War College and the son of West Point’s formidable Dennis Mahan. Mahan the elder had urged officers to study the history of land battles so as to learn and master the tactics that could lead to victory. Mahan the younger steered a similar course, but his concern lay with grand naval strategy. Drawing on the history of major navies, he gave definition to the concept of sea power: that whoever could control the sea would master the overall situation.