on the high seas. Congress primarily commissioned privateers to reduce costs and to take advantage of the large proportion of colonial sailors found in the British Empire. Overall, they included 1,700 ships that successfully captured 2,283 enemy ships to damage the British effort and to enrich themselves with the proceeds from the sale of cargo and the ship itself. About 55,000 sailors served aboard American privateers during the war. France At the beginning of the war, the Americans had no major international allies, as most nation-states watched and waited to see how developments would unfold in British North America. Over time, the Continental Army acquitted itself well in the face of British regulars and their hired German soldiers known to all European great powers. Battles such as the Battle of Bennington, the Battles of Saratoga, and even defeats such as the Battle of Germantown, proved decisive in gaining the attention and support of powerful European nations including France and Spain, and the Dutch Republic; the latter moved from covertly supplying the Americans with weapons and supplies to overtly supporting them. The decisive American victory at Saratoga convinced France, who was already a long-time rival of Britain, to offer the Americans the Treaty of Amity and Commerce. The two nations also agreed to a defensive Treaty of Alliance to protect their trade and also guaranteed American independence from Britain. To engage the United States as a French ally militarily, the treaty was conditioned on Britain initiating a war on France to stop it from trading with the US. Spain and the Dutch Republic were invited to join by both France and the United States in the treaty, but neither made a formal reply. On June 13, 1778, France declared war on Great Britain, and it invoked the French military alliance with the US, which ensured additional US privateer support for French possessions in the Caribbean. Washington worked closely with the soldiers and navy that France would send to America, primarily through Lafayette on his staff. French assistance made critical contributions required to defeat General Charles Cornwallis at Yorktown in 1781. British strategy The British military had considerable experience of fighting in North America, most recently during the Seven Years' War which forced France to give up New France in 1763. However, in previous conflicts they benefited from local logistics, as well as support from the colonial militia, which was not available