The capitals of the Union and the Confederacy lay only a hundred miles apart, so the steep, tangled, river-laced terrain around and between Washington and Richmond became the principal battleground of the War Between the States. Mighty but mishandled, Yankee armies were repeatedly savaged by smaller but well-led Rebel forces, and between the major battles soldiers marched and countermarched, raided and reconnoitered, patrolled and ambushed. And loyalties did not divide so neatly as the state lines that had suddenly been proclaimed national borders, so that neighbor betrayed neighbor, and vigilantes rode. From the spring of 1861 to the spring of 1865, few households in the region could pass a night in the calm certainty that no hostile gun or torch was nigh. Any attempt to consider the course of the struggle is complicated by hundreds of skirmishes and minor engagements, plus such complex sideshows as the several SHENANDOAH VALLEY CAMPAIGNS (Winchester changed hands about six dozen times). HARPERS FERRY, dominating the Blue Ridge water gap, distracted a whole series of commanders on both sides; somehow, possession of this key point usually hurt whichever side held it. The definitive Old Dominion tour guide is the paperback Civil War Sites in Virginia by James I. Robertson Jr. (University of Virginia Press), available for about $5 at most visitor centers and tourist shops. But the main threads of the conflict are not difficult to follow, with the help of the films, maps and other exhibits of the National Park Service visitor centers at the major battlefields. Once you've grasped the outlines of the action, it's fascinating to go over the field itself, on foot if possible. With a little luck you'll run into one of the countless, and generally garrulous, Civil War buffs who constantly roam the grounds. Some of them can recount every movement of every unit in a vast engagement.