Final answer:
In December of 1777, following the pivotal victory at Saratoga and the alliance with France, Washington led his troops to Valley Forge for their winter encampment.
Step-by-step explanation:
After the victory at Saratoga, which convinced the French to form an alliance with America, George Washington brought his men to Valley Forge in December of 1777. The American victory at the Battle of Saratoga was a significant turning point in the Revolutionary War, leading to French military support and the eventual defeat of Britain. Valley Forge served as the winter encampment for Washington's troops during the harsh winter of 1777-1778, where the Continental Army faced severe conditions but emerged as a more disciplined force.