General George Washington's strategic decisions also improved the situation for Gates' army. Washington was most concerned about the movements of General Howe. He was aware that Burgoyne was also moving, and he took some risks in July. He sent aid north in the form of Major General Benedict Arnold, his most aggressive field commander, and Major General Benjamin Lincoln, a Massachusetts man noted for his influence with the New England militia. He ordered 750 men from Israel Putnam's forces defending the New York highlands to join Gates' army in August, before he was certain that Howe had indeed sailed south. He also sent some of the best forces from his own army: Colonel Daniel Morgan and the newly formed Provisional Rifle Corps, which comprised about 500 specially selected riflemen from Pennsylvania, Maryland, and Virginia, chosen for their sharpshooting ability. This unit came to be known as Morgan's Riflemen.