Could the Americans have won without France, and what did it cost the French?

The sources suggest it was very hard. Historian Edmund Morgan called Saratoga a great turning point because it won for Americans the foreign assistance that was the last element needed for victory. France's direct help is described as a major and decisive contribution to the United States' eventual victory and independence. And the final blow, at Yorktown in 1781, was struck by American and French armies together, with a French fleet cutting off the sea.

France had reasons of its own. Having lost its North American colony to Britain in the Seven Years' War, it sought to weaken Britain by helping the American insurgents. At first the help was covert: from spring 1776, mostly gunpowder sent through a front company, and estimates put French-supplied arms in the Saratoga campaign at up to 90%.

The American victory at Saratoga, and the surrender of a British army there, persuaded France to enter the war as an ally. In February 1778 it recognised the United States with a Treaty of Alliance, and Britain declared war on France soon after. At Yorktown, the French fleet under de Grasse blocked any reinforcement or escape by sea for Cornwallis, and more than 7,000 British soldiers were captured.

The cost was heavy. France accumulated over 1 billion livres in debt, which significantly strained its finances. According to one account, the French government's failure to control spending, in combination with other factors, led to unrest that culminated in a revolution six years after the war ended.