Cornwallis moved carelessly. He left American units, such as the one led by Francis Marion (called the "Swamp Fox"), in his rear. The American general Nathanael Greene noticed this right away. He broke up his command into smaller units in order to plague Cornwallis. Finally the two armies met at the Battle of Guilford Court House, which neither army won. During this time Cornwallis was not sending messages to Clinton telling him where he was. After Guilford Court House, Cornwallis moved to the coast of North Carolina to rest his men. Then, again without orders, he decided to march north to Virginia. Frustrated by this, Clinton sent Cornwallis a number of contradictory messages. Most of them were worded as suggestions rather than orders. But he did order Cornwallis to find a defensible position. This was so he could be evacuated by the Royal Navy, possibly to Philadelphia. Cornwallis decided on the community of Yorktown and his men started building defenses there in August of 1781 to wait for the Navy.