When Robert E. Lee pressed so hard to invade the North, it was not only to feed his starving men from the rich provender of farms untouched by combat. It was also to give the Northern public the despairing feel of enemy occupation, and get them voting for peace in the upcoming mid-term elections.

Yet not even he could have foreseen that a cornfield at Antietam Creek, beside Sharpsburg, Maryland, would soon be so littered with bodies that a man could walk across it without ever touching the ground. A Confederate win here might have ended the war.

Meanwhile those recent victories of Lee's had demoralised the Army of the Potomac so much that Union officers were starting to write defeatist letters home. Only one general could restore the men's fighting spirit, and that was George McClellan, implacably distrusted by Lincoln, who appointed him with deep reluctance.

The story of Lee's battle-plan falling into McClellan's hands is well-known, even though we still don't know how it happened, or why McClellan delayed a fatal twelve hours before taking-up what would have been an impregnable position. Instead the two armies locked into a fight that inflicted more casualties in one day than any other battle fought on American soil. And after a glorious summer of victories, Lee found himself leading his bedraggled army back to Virginia.

'Decisive' can mean two things. As a contest, the Battle of Antietam had no clear winner, and was thus indecisive. As an event, it changed human history, and proved more decisive than any battle of the war. For this longed-for Union win, however narrow, had given Lincoln the credibility to issue his Emancipation Proclamation (notionally freeing all Southern slaves), without making it sound like a counsel of despair. From here on, it was an abolitionist war, and any hope of Britain and France aiding the South was gone with the wind. This political slant may explain the rather odd title 'Lincoln and Lee at Antietam'.

The story is vividly presented here, along with well-informed commentators, one of them a Princeton scholar, another the long-serving local battlefield tour-guide. The huge cast of actors look realistic enough (no textile-firm is ever going to go bust making Civil War uniforms!) and the two generals are suitably cast, as is Lincoln. The mention of field-hospital manager Clara Barton is so brief that it can sound a bit token-female, though we do also hear some of the outspoken remarks of the local townswomen on the arrival of the armies. I never knew that Lee was recovering from injuries to both his hands, and could neither write orders nor hold the reins of his horse. Finally, it's good to hear a defence of poor old Burnside, ridiculed up hill and down dale by historians, yet who can be shown as the only Union general at Antietam who secured the objective that he was ordered to - still known as Burnside Bridge.

It's essentially a reenactment of the three major phases of the Battle of Antietam, supplemented by occasional maps, quotes from letters and reports of the time, and a handful of familiar experts contributing descriptions and analyses of the battle and the personalities in command.

It's well put together. The battle scenes are exciting and the interpretive comments on point. It was a horrible fight, with George B. McLellan in charge of the Union forces and Robert E. Lee commanding the Confederates. And the battle was important too, not adventitious. This was Lee's first attempt to invade the north, relieving Virginia of the burden of carrying the war, threatening the cities of Baltimore and Washington, and perhaps, by securing a victory, of enticing Europe to broker a peace between the North and the South. On the other hand, Lincoln needed to stop Lee and be handed a victory as an excuse to issue the Emancipation Proclamation, which freed some of the slaves. Without a victory, such a move would have been seen as an act of desperation.

Well, nobody won. Lee's battle plan was most improbably revealed to McLellan by accident but it took the general a day and a half to get his rear end in gear. McLellan had several opportunities to reenforce breakthroughs but was wary of committing his reserves because he thought, mistakenly, that Lee was holding back his own. Lee was outnumbered and in the process of losing until the late arrival of reenforcements. The wind up was that Lee trudged back across the Potomac with his ragged army decimated, and McLellan hurried after him in slow motion. McLellan's last horses crossed the Potomac in pursuit nine days after Lee had gone. Still, McLellan claimed a great victory and Lincoln had to go along with it in order to issue the Emancipation Proclamation. That put an end to the idea of European intervention. No country was likely to intercede on behalf of the Confederacy now that the US has banned slavery.

Despite the momentousness of the battle and the gravity of the issue, it's kind of a weak documentary. It's narrated by Ronald F. Maxwell. I understand he directed the feature film "Gettysburg", and he did a professional job, but he does not have a dramatic voice. Nor does he sound matter-of-fact, resigned, sad, like David McCullough who provided the narration for Ric Burns' superb "The Civil War." The written narration is fine, and the quotations are appropriate, but the voices reading them are not. Robert E. Lee, a gentleman through and through, who rarely referred to Northerners as "the enemy" but preferred "these people," is made sometimes to sound angry and resentful. Some of his lieutenants sound enraged. Quotes from the letters of ordinary soldiers are sometimes read with too much emotion, sometimes quivering with fear and rising at the end into a falsetto. On top of that, Robert E. Lee looks less like Robert E. Lee than like Santa Claus after a quick trip to the barber. McClellan is a good likeness, but Lincoln has a bulbous nose and rough complexion.

It's not clear where the title came from. Lee is present often enough but we scarcely see Lincoln until the last few climactic moments. Come to think of it, I understand that Steven Spielberg's new movie, "Lincoln," deals with this same critical period in the president's life.

It's a worthwhile sketch of the battle but there are better descriptions around.