In late 1775 Frederick II signed an agreement with King George III of Great Britain to supply him with troops for use in North America in suppressing the rebellion that had broken out in the Thirteen Colonies. The troops supplied by Frederick included the Leib Regiment, and Ewald arrived in New York City in October 1776. Sent forward to New Rochelle, his jäger company was given a lead position in the army of General William Howe, and was first engaged in the 28 October Battle of White Plains. His position in the advance became quite normal for his company, which was consequently often engaged in skirmishes and the leading edges of battles. Ewald served with some distinction in the New Jersey and Philadelphia campaigns, where he was involved in (among others) battles at Mount Holly, Brandywine, and Germantown. On the direction of General Charles Cornwallis, Ewald developed a plan of attack against a Continental Army position at Bound Brook, New Jersey in March 1777. In the April battle, the Continentals were surprised, and their commander, Benjamin Lincoln, narrowly avoided capture.