The battle of Lexington and Concord occurred when Thomas Gage sent British officers to confiscate minutemen weapons. He heard that the minutemen were storing weapons and unknowingly sent his men into an ambush. The minute men had received word they were coming and were ready for the British.
The battle of Valley Forge happend in the winter of 1777-1778. No actual battle was fought. The patriot soldiers were under prepared for the winter and died of exposure, malnutrion and illness.
The battle of Yorktown was the last major battle of the Revolutionary War. It was where the British general Charles Cornwallis surrendered to the Patriots. It brought about the "Treaty of Paris" which made the British officially recognize the united states.