No Independence Without Foreign Intervention
Washington could never have achieved American independence without foreign recognition and military aid, and in 1861 the American Confederacy sought assistance from England and France to achieve independence. This was still a possibility by late 1863, but Lincoln and Seward took advantage of Russian animosity toward England and France by inviting the two-ocean Russian fleet into New York and San Francisco harbors for an extended eight-month stay.  This let Europe know that their merchant fleets would be at risk should they dare to recognize Southern independence.
Bernhard Thuersam, Director
Cape Fear Historical Institute  
No Independence Without Foreign Intervention:
“The French had now 36 [ships] of the line – an overpowering force as against the British, even should include a reinforcement of six ships f the line just arrived at New York under Admiral Digby – news which came near sending [French Admiral] de Grasse again to sea in search of the enemy. But the fates were with the allies.
It was an incapable British admiral that saved the situation and brought de Grasse back to a position he should never have left. As it was, by September 28 the combined armies [of French and Americans] were in front of Yorktown, partly transported from the headwaters of the Chesapeake by French frigates sent to Annapolis, partly by the ordinary land route; and the loss of Cornwallis with his 7,000 men, and the complete restoration of continental authority in the South had become a certainty. The surrender took place on October 19.
The fact that Washington marched south with but 2,000 Continentals and 4,000 French alone shows the supreme importance of the French fleet. Without it there would had been no American independence. There could have been no more complete indication of Washington’s dictum, that “In any operation, and under all circumstances, a decisive naval superiority is to be considered a fundamental principle and the basis upon which every hope of success must depend.”
(Sea Power: The Decisive Factor in Our Struggle for Independence, French E. Chadwick, Annual Report of the American Historical Association, 1915, AHA, 1917, pp. 186-189)