February 6, 1778 – American and French representatives sign two treaties in Paris: a Treaty of Amity and Commerce and a Treaty of Alliance. France now officially recognizes the United States and will soon become the major supplier of military supplies to Washington's army. Both countries pledge to fight until American independence is won, with neither country concluding any truce with Britain without the other's consent, and guarantee each other's possessions in America against all other powers.
The American struggle for independence is thus enlarged and will soon become a world war. After British vessels fire on French ships, the two nations declare war. Spain will enter in 1779 as an ally of France. The following year, Britain will declare war on the Dutch who have been engaging in profitable trade with the French and Americans. In addition to the war in America, the British will have to fight in the Mediterranean, Africa, India, the West Indies, and on the high seas. All the while facing possible invasion of England itself by the French.
February 23, 1778 – Baron von Steuben of Prussia arrives at Valley Forge to join the Continental Army. He then begins much needed training and drilling of Washington's troops, now suffering from poor morale resulting from cold, hunger, disease, low supplies and desertions over the long, harsh winter.
March 16, 1778 – A Peace Commission is created by the British Parliament to negotiate with the Americans. The commission then travels to Philadelphia where its offers granting all of the American demands, except independence, are rejected by Congress.
May 8, 1778 – British General Henry Clinton replaces Gen. Howe as commander of all British forces in the American colonies.
May 30, 1778 – A campaign of terror against American frontier settlements, instigated by the British, begins as 300 Iroquois Indians burn Cobleskill, New York.
June 18, 1778 – Fearing a blockade by French ships, British Gen. Clinton withdraws his troops from Philadelphia and marches across New Jersey toward New York City. Americans then re-occupy Philadelphia.
June 19, 1778 – Washington sends troops from Valley Forge to intercept Gen. Clinton.
June 27/28, 1778 – The Battle of Monmouth occurs in New Jersey as Washington's troops and Gen. Clinton's troops fight to a standoff. On hearing that American Gen. Charles Lee had ordered a retreat, Gen. Washington becomes furious. Gen. Clinton then continues on toward New York.
July 2, 1778 – Congress returns once again to Philadelphia.
July 3, 1778 – British Loyalists and Indians massacre American settlers in the Wyoming Valley of northern Pennsylvania.
July 8, 1778 – Gen. Washington sets up headquarters at West Point, New York.
July 10, 1778 – France declares war against Britain.
August 8, 1778 – American land forces and French ships attempt to conduct a combined siege against Newport, Rhode Island. But bad weather and delays of the land troops result in failure. The weather-damaged French fleet then sails to Boston for repairs.
September 14, 1778 – Ben Franklin is appointed to be the American diplomatic representative in France.
November 11, 1778 – At Cherry Valley, New York, Loyalists and Indians massacre over 40 American settlers.
December 29, 1778 – The British begin a major southern campaign with the capture of Savannah, Georgia, followed a month later with the capture of Augusta.