Pulitzer Prize History of Civil War. BOOKS

BATTLE CRY OF FREEDOM: THE CIVIL WAR ERA by James M. McPherson, New York: Oxford University Press, 904 pp.,

$29.95 cloth, Ballantine paperback $14.95

TWO and a half months before the presidential election of 1864, Abraham Lincoln wrote in a brief memo to himself: ``It seems exceedingly probable that this administration will not be reelected.'' Then he went through a ritual of sorts: without showing what he had written, he asked his Cabinet members to sign the backside of the sheet. Next he sealed the document and ``pasted it up in so singular style,'' to quote his secretary John Hay, ``that it required some cutting to get it open.'' That cutting open in a Cabinet meeting did not take place until Lincoln had been reelected.

In another five months the war was over, the North victorious. Then the bullet of John Wilkes Booth sealed Lincoln's fate - and also his reputation as the greatest president in American history.

But Lincoln had been an astute politician, and his judgment in the late summer of 1864 about the great likelihood of his defeat was sound. Had the presidential elections taken place in August, the ``Savior of the Union'' and the ``Great Emancipator'' would be known to history as one of the worst American leaders, an eloquent but tragic fool. The United States - and the world - would be a very different place today.

What channeled history in the course we do know was a change in the fortunes of war. As Sherman battered at the gates of Atlanta, Jefferson Davis replaced his tenacious Gen. Joseph Johnston with the brash John Bell Hood. In short order thereafter, Atlanta fell. Simultaneously, Jubal Early's Confederates, who had reached the outskirts of Washington earlier that summer, were destroyed by Phil Sheridan in the Shenandoah Valley, as was much of the valley itself.

The North was again willing to carry on with its terrible burden and reelect Lincoln. No wonder his Second Inaugural Address spoke of ``the progress of our arms, upon which all else chiefly depends....''

History, James McPherson's ``Battle Cry of Freedom'' argues, often hangs by a thin thread. He calls this ``contingency.''

``At numerous critical points during the war things might have gone altogether differently,'' he writes. The crisis of 1864 is only one of several such critical moments McPherson depicts. Earlier, in the summer of 1862, the Northern Army of the Potomac reached within five miles of the Confederate capital of Richmond, and in the West, too, the Union seemed on the verge of triumph. Vigorous counter-offensives, however, helped the cause of Southern independence.

Later that fall, the Confederates invaded key border states. Their victories could have made the Northern cause untenable. But victories failed to come as federal forces held the fields at Antietam, on a day that remains the bloodiest in American history, and also those in Kentucky. The Europeans retreated from intervention, the Northern voters refused to repudiate the Republicans in the fall elections, and Lincoln went ahead with emancipation.

The South rose again in late 1862 and 1863, to a high tide, but at Gettysburg, Vicksburg, and Chattanooga, it was thrown back. Along the way, one of its finest soldiers wrote in his diary: ``The Confederacy totters to its destruction.'' This anguish of the Northern-born ordnance chief Josiah Gorgas was premature. For in 1864, Lee fought Grant to a standstill in Virginia and a weary North wanted peace. Lincoln seemed on the verge of defeat and the US on the verge of extinction.

If historians like to explain the past in terms of large impersonal forces, the general public tends to lean in the opposite direction. McPherson reaches a sensible compromise: contingency. Many large forces come into play (though some in academe will focus on absences), above all freedom and its antithesis, slavery. Individuals and events are present, too, however, as is the caprice of history itself. Matters military dominate. But in sharp contrast to historian Bruce Catton, McPherson also covers political, economic, and social developments, and the antebellum period commands one-third of the text.

And what sprightly text this is, what excellent narrative, combining a synthesis of modern scholarship with McPherson's own acute insights. Of course experts and buffs will continue to refight every battle. Room for disagreement remains. For example, the reader sees the old federal union revolutionized into an ever more centralized nation. Yet Robert V. Bruce's Pulitzer Prize-winning study, ``The Launching of Modern American Science, 1846-1876'' (1988), shows that during the same period US science headed in the opposite direction, and over the long run fared well indeed. Could that have happened to the US as a whole?

McPherson, too, asks: ``Was the liberation of four million slaves and the preservation of the Union worth the cost of the war?'' In dead bodies alone, that cost matched the dead of all other American wars combined. ``Battle Cry of Freedom'' concludes: ``That question too will probably never cease to be debated - but in 1865, few black people and not many Northerners doubted the answer.''