The French partnership throughout the revolution was indeed critical. Without it, it's unlikely the Thirteen Colonies would have prevailed.

France's involvement turned what would have been a localized, colonial rebellion into a potentially global conflict. France was Britain's primary imperial rival, with the reputation as the finest army in Europe. Britain's fears about the rebellion igniting a wider global conflict weighed heavily on them, especially after defeat in Saratoga.

France's contributions began with political thought. As tensions emerged in the 1760's over taxation and representation, the colonists devoured French political philosophy. Philosopher Jean-Jacques Rousseau's The Social Contract described how sovereignty resided in men, not in a monarch. Such powerful ideas formed the underpinnings of revolutionary thought and provoked its leaders into action.

The Continental Congress made secret overtures to France in 1775 - 1776 to provide clandestine financial aid, supplies and weapons. America was able to secure clothing, arms and ammunition for 25,000 soldiers as the war began.

More importantly, it obtained open-ended credit from France in order to finance the war, to the tune of 1.3 billion livres in total by war's end (an astronomical $13B in today's US dollars). Britain's fleet was strangling America's Atlantic trade and these funds were a lifeline that kept the economy from collapsing and kept the Continental Army supplied, armed and in the field.

The situation had reached a stalemate by 1777. The British could not crush the rebellion, but the Patriots were unable to dislodge the British. Politically, America needed a decisive win soon, not only to demonstrate its resolve to Britain -- but to the European powers whose trade would help America survive after the war. The revolution's leaders knew that economic autonomy would secure its independence. French support would be the means to achieve it.

This opportunity came at Saratoga. It was a significant military victory for America, but it was also in some ways a French one: 90% of Continental troops in the battle carried French arms and all their gunpowder came from France.

This victory achieved what the colonists wanted -- to show Europe (esp. France) that it could fight -- and win. They needed to secure economic and diplomatic support to confirm any independence won in battle. France responded with a Treaty of Alliance and Treaty of Amity and Commerce in 1778. With this treaty, America gained political legitimacy in the eyes of Europe's statesmen, who could no longer dismiss the rebellion as a mere insurrection of British subjects.

About 12,000 French soldiers served in the rebellion, which included Lafayette and the comte of Rochambeau. 22,000 French naval personnel aboard 63 warships helped to challenge British dominance in the sea and won a decisive victory over the British fleet in the Battle of Chesapeake in 1781.

In the Battle of Yorktown, there were about 6,000 American regular troops -- but more than 7,500-8,000 French ones, in addition to 29 French warships. The victory forced the British to capitulate and negotiate peace terms. Both France and America refused to negotiate separate treaties with Britain, but only make terms in tandem.

When you consider how pivotal Saratoga and Yorktown were to the success of the revolution, France's aid throughout the conflict cannot be discounted. Without France, the Americans would have been hard-pressed to prolong the war on its own, as Britain poured more imperial resources and regular forces into the war from 1778 onward.

France's significant financial aid kept the Continental Army in the field and, critically, helped America's economy to better weather the crippling British naval blockade. France's formal involvement with the 1778 treaties and during the peace negotiations in Paris gave the rebellion much needed political legitimacy in the eyes of Europe and opened paths to future trade.