At Wilmington, the British general faced a serious problem. Instead of remaining in North Carolina, he was determined to march into Virginia, justifying the move on the ground that until Virginia was reduced, he could not firmly hold the more southerly states he had just overrun. General Clinton sharply criticized the decision as unmilitary, and as having been made contrary to his instructions. To Cornwallis he wrote in May: "Had you intimated the probability of your intention, I should certainly have endeavoured to stop you, as I did then as well as now consider such a move likely to be dangerous to our interests in the Southern Colonies." For three months, Cornwallis raided every farm or plantation he came across, from which he took hundreds of horses for his Dragoons. He converted another 700 infantry to mounted duties. During these raids, he freed thousands of slaves, of whom 12,000 joined his own force.