After taking over as commander-in-chief of the Continental Army, Washington immediately left to oversee the siege of Boston and took command of an army of barely 14,500 men, mostly untrained for combat. To overcome a dismal shortage of gunpowder, he ordered raids on the British arsenal in the countryside. He moved the American artillery on Dorchester Heights, overlooking the city, thus making it impossible for the British to enter the city, thereby cutting off their supplies from adjoining regions.