By the evening of October 6 all was in readiness for the opening of the First Allied Siege Line—a series of positions which, together with terrain advantages, completely encircled the British works and brought men and artillery within firing range of the enemy. The first line was based on the York River southeast of Yorktown and extended westward just above the headwaters of Wormley Creek, across the York-Hampton Road, to Yorktown Creek, which in a real sense functioned as a continuation of the line. The first line was about 2,000 yards long and was supported by four redoubts and five batteries. Its average distance from the main British works was about 800 yards, although, on the right, this was somewhat greater because of two detached British Redoubts, Nos. 9 and 10. About half of this line, the right or York River end, was assigned to American units; the left was built and manned by the French. At dusk on October 6, more than 4,000 allied troops paraded and marched to their assigned stations. The entrenching party, 1,500 strong, carrying knapsacks, guns, and bayonets, as well as shovels, found a line of split pine strips already on the ground. They had been placed by the engineers to mark the line where the digging was to begin. Twenty-eight hundred soldiers lay under arms close at hand to repel attack should it come. Evidently the British were caught unawares, for their guns were not particularly active. The night was dark and cloudy, with a gentle rain falling—a factor which may have aided the troops who were being directed by General Lincoln and the Baron de Viomenil. By morning, the work was well advanced, enough to give those in the trenches protection from British gunners. During the next few days, with precision and dispatch, unit followed unit on fatigue duty as the trenches, redoubts, and batteries were brought to perfection. Major General von Steuben, one of the few veterans of siege warfare in the American wing, had a leading role in planning and constructing the siege works. Brigadier General Knox, with the American artillery, played a significant part, too, since effective gunnery was a prime prerequisite to success in the operation.