Many roads converge at this point. A trifle over two miles south of the town there are two bold and commanding hills--Round Top and Little Round Top. From these a line of hills extends toward the town, commanding the lower ground to the east and west. This is called Cemetery Ridge, and is not to be confounded with Seminary Ridge, presently to be mentioned. Cemetery Ridge, just before it reaches the town, trends off to the east and ends in Culp's Hill. West of the town is another and higher ridge, also running north and south, called Seminary Ridge. Just west of these high grounds is Willoughby Run, a little creek which afforded opportunity for attack and defense. When Lee learned that Meade, instead of sitting down to the defense of Washington, was advancing against his communications, he ordered his army to concentrate at Gettysburg for a decisive battle. Meade in the meanwhile was pushing his columns to that point. Here were two masters of the game of war, who, while opposing each other, were agreed that Gettysburg was the key to the situation. The strategic value of that point was equally apparent to both. Lee, being left in the dark by Stuart's absence, was slowly advancing in detachments, in order to subsist his army upon the country, confident that his enemy was still lingering around Washington and that he had himself ample time in which to seize the commanding positions in advance of the foe's approach. Meade, meanwhile, was perfectly informed of Lee's movements and was hourly quickening his march. When the head of Lee's column under Ewell reached the neighborhood of Gettysburg on the first of July, it encountered not only the Federal cavalry, which it had expected to find there and to brush aside without difficulty, but the whole of Meade's advance corps--artillery and infantry--under Reynolds, while another corps under Howard was hurrying up in support. Seizing upon the line of Willoughby Run the Federals undertook to hold it and the hills in rear of it against the enemy's assault. Ewell, expecting to encounter no resistance except such as the cavalry and perhaps some brigades of Pennsylvania militia, could offer, advanced confidently only to find his way disputed by some of the best veteran corps of the Army of the Potomac. Reynolds, commanding the Federal advance, was killed early in the action and Doubleday succeeded him. Howard presently superseded Doubleday in chief command and later Hancock replaced Howard.