General Lincoln was indefatigable in improving the time which the slow progress of the royal army afforded him. Six hundred slaves were employed in constructing or repairing the fortifications of the town; vigorous though not very successful measures were taken to bring the militia into the field; and all the small detachments of regular troops were assembled in the capital. The works which had been begun on Charleston Neck when General Prevost threatened the place were resumed. A chain of redoubts, lines, and batteries was formed between the Cooper and Ashley rivers. In front of each flank the works were covered by swamps extending from the rivers; those opposite swamps were connected by a canal; between the canal and the works were two strong rows of abattis, and a ditch double picketed, with deep holes at short distances, to break the columns in case of an assault. Toward the water, works were thrown up at every place where a landing was practicable. The vessels intended to defend the bar of the harbor having been found insufficient for that purpose, their guns were taken out and planted on the ramparts, and the seamen were stationed at the batteries. One of the ships, which was not dismantled, was placed in the Cooper river to assist the batteries, and several vessels were sunk at the mouth of the channel to prevent the entrance of the royal fleet. Lincoln intended that the town should be defended until such reinforcements would arrive from the North as, together with the militia of the State, would compel Clinton to raise the siege. As the regular troops in the town did not exceed 1,400, a council of war found that the garrison was too weak to spare detachments to obstruct the progress of the royal army. Only a small party of cavalry and some light troops were ordered to hover on its left flank and observe its motions. While these preparations for defense were going on in Charleston the British army was cautiously but steadily advancing toward the town. As he proceeded Clinton erected forts and formed magazines at proper stations, and was careful to secure his communications with those forts and with the sea. All the horses of the British army had perished in the tedious and stormy voyage from New York to Savannah, but on landing in South Carolina Clinton procured others to mount his dragoons, whom he formed into a light corps, under the command of Lieutenant-Colonel Tarleton. That officer was extremely active in covering the left wing of the army and in dispersing the militia. In one of his excursions he fell in with Lieut.-Col. William Washington, who commanded the remnant of Baylor's regiment, and who beat him back with loss. On the 20th of March (1780) the British fleet, under Admiral Arbuthnot, consisting of 1 ship of 50 guns, 2 of 44 each, 4 of 32 each, and an armed vessel, passed the bar in front of Rebellion Road, and anchored in Five Fathom Hole.