An express carrying letters, communicating to congress the result of his consultations on this subject, with the commanders of the land and naval forces of France, was intercepted in Jersey. The interesting disclosure made by these letters, alarmed Sir Henry Clinton for the safety of New York, and determined him to require the return of a part of the troops in Virginia. Supposing himself too weak, after complying with this requisition, to remain at Williamsburg, Lord Cornwallis took the resolution of retiring to Portsmouth. In pursuance of this resolution, he marched from Williamsburg and encamped in such a manner as to cover the ford into the island of Jamestown. On the same evening, the Queen's rangers crossed over into the island; and the two succeeding days were employed in passing over the baggage. The morning after the evacuation of Williamsburg, Lafayette changed his position, and pushed his best troops within nine miles of the British camp, with the intention of attempting their rear, when the main body should have passed into Jamestown. [Sidenote: July 6.] Suspecting his design, Lord Cornwallis encamped the greater part of his army on the main land as compactly as possible, and displayed a few troops on the island in such a manner as, in appearance, to magnify their numbers. All the intelligence received by Lafayette concurred in the representation that the greater part of the British army had passed over to the island in the night. Believing this to be the fact, he detached some riflemen to harass their out-posts, while he advanced at the head of the continental troops in order to cut off the rear. Every appearance was calculated to countenance the opinion he had formed. The British light parties were drawn in, and the piquets were forced by the riflemen without much resistance, but an advanced post which covered the encampment from the view of the Americans, was perseveringly maintained, though three of the officers commanding it were successively picked off by the riflemen. Lafayette, who arrived a little before sunset, suspected from the obstinacy with which this post was maintained, that it covered more than a rear guard, and determined to reconnoitre the camp, and judge of its strength from his own observation.[78] It was in a great measure concealed by woods; but from a tongue of land stretching into the river, he perceived the British force to be much more considerable than had been supposed, and hastened to call off his men. [Footnote 78: Correspondence with Lafayette.] [Sidenote: Action near Jamestown.]