De Grasse arrived at Cap-Français on 15 August. He immediately dispatched his response to Rochambeau's note, which was that he would make for the Chesapeake. Taking on 3,200 troops, De Grasse sailed from Cap-Français with his entire fleet, 28 ships of the line. Sailing outside the normal shipping lanes to avoid notice, he arrived at the mouth of the Chesapeake Bay on August 30, and disembarked the troops to assist in the land blockade of Cornwallis. Two British frigates that were supposed to be on patrol outside the bay were trapped inside the bay by De Grasse's arrival; this prevented the British in New York from learning the full strength of de Grasse's fleet until it was too late.