Cap-Français on August 5, beginning a deliberately slow route north through a little-used channel in the Bahamas. British decisions The movement of the French army to the New York area caused General Clinton a great deal of concern; letters written by Washington that Clinton had intercepted suggested that the allies were planning an attack on New York. Beginning in June he wrote a series of letters to Cornwallis containing a confusing and controversial set of ruminations, suggestions, and recommendations, that only sometimes contained concrete and direct orders. Some of these letters were significantly delayed in reaching Cornwallis, complicating the exchange between the two. On June 11 and 15, apparently in reaction to the threat to New York, Clinton requested Cornwallis to fortify either Yorktown or Williamsburg, and send any troops he could spare back to New York. Cornwallis received these letters at Williamsburg on June 26. He and an engineer inspected Yorktown, which he found to be defensively inadequate. He wrote a letter to Clinton indicating that he would move to Portsmouth in order to send troops north with transports available there. On July 4 Cornwallis began moving his army toward the Jamestown ferry, to cross the broad James River and march to Portsmouth. Lafayette's scouts observed the motion, and he realised the British force would be vulnerable during the crossing. He advanced his army to the Green Spring Plantation, and, based on intelligence that only the British rear guard was left at the crossing, sent General Wayne forward to attack them on July 6. In reality, the earl had laid a clever trap. Crossing only his baggage and some troops to guard them, he sent "deserters" to falsely inform Lafayette of the situation. In the Battle of Green Spring, General Wayne managed to escape the trap, but with significant casualties and the loss of two field pieces. Cornwallis then crossed the river, and marched his army to Suffolk. Cornwallis again detached Tarleton on a raid into central Virginia. Tarleton's raid was based on intelligence that supplies might be intercepted that were en route to General Greene. The raid, in which Tarleton's force rode in four days, was a failure, since supplies had already been moved. (During this raid, some of Tarleton's men were supposedly in a minor skirmish with Peter Francisco, one of the American heroes of Guilford Court House.) Cornwallis received another letter from General Clinton while at