The war lasted for six years. The Americans were poorly trained, did not have enough guns, and had to fight a much stronger army. However, when the French decided to help the American the war started to go in their favour. The British army under Lord Cornwallis finally surrendered(gave up fighting) at Yorktown in 1781. By the peace treaty of 1783, the British agreed to accept American independence, and all the land from the Appalachians to the Mississippi was put under the control of the Americans. The United States became a nation.