Henry Clinton. On June 17, they seized the Charlestown Peninsula at the Battle of Bunker Hill, a frontal assault in which they suffered over 1,000 casualties. Dismayed at the costly attack which had gained them little, Gage appealed to London for a larger army to suppress the revolt, but instead was replaced as commander by Howe. On June 14, 1775, Congress took control of Patriot forces outside Boston, and Congressional leader John Adams nominated George Washington as commander-in-chief of the new Continental Army. Washington previously commanded Virginia militia regiments in the French and Indian War, and on June 16, John Hancock officially proclaimed him "General and Commander in Chief of the army of the United Colonies." He assumed command on July 3, preferring to fortify Dorchester Heights outside Boston rather than assaulting it. In early March 1776, Colonel Henry Knox arrived with heavy artillery acquired in the Capture of Fort Ticonderoga. Under cover of darkness, on March 5, Washington placed these on Dorchester Heights, from where they could fire on the town and British ships in Boston Harbor. Fearing another Bunker Hill, Howe evacuated the city on March 17 without further loss and sailed to Halifax, Nova Scotia, while Washington moved south to New York City. Beginning in August 1775, American privateers raided towns in Nova Scotia, including Saint John, Charlottetown, and Yarmouth. In 1776, John Paul Jones and Jonathan Eddy attacked Canso and Fort Cumberland respectively. British officials in Quebec began negotiating with the Iroquois for their support, while US envoys urged them to remain neutral. Aware of Native American leanings toward the British and fearing an Anglo-Indian attack from Canada, Congress authorized a second invasion in April 1775. After defeat at the Battle of Quebec on December 31, the Americans maintained a loose blockade of the city until they retreated on May 6, 1776. A second defeat at Trois-Rivières on June 8 ended operations in Quebec. British pursuit was initially blocked by American naval vessels on Lake Champlain until victory at Valcour Island on October 11 forced the Americans to withdraw to Fort Ticonderoga, while in December an uprising in Nova Scotia sponsored by Massachusetts was defeated at Fort Cumberland. These failures impacted public support for the Patriot cause, and aggressive anti-Loyalist policies in the New England colonies alienated the Canadians. In Virginia, an attempt by Governor Lord Dunmore to seize militia stores on April 20, 1775, led