Date: June 28, 1778
The Battle of Monmouth wasn't particularly significant strategically, but it was an important proving ground for Washington and the Continental Army. It was also a near-disaster. But I'm getting ahead of myself, and that's naughty.
Once the British learned that the French had joined the Revolutionary War, British troops were ordered to withdraw from Philadelphia and march to New York City. That's quite a march. I bet they couldn't wait for the invention of the motor car.
The Continental Army was just finishing its winter at Valley Forge and George Washington was anxious to try his newly-trained troops. He decided to attack the British column in an attempt to delay it - or stop it entirely.
Washington chose Charles Lee to lead the advance guard in the attack. At first Lee said no, saying that the British troops should be left alone. However, when Washington ignored his protests and offered the command to the Marquis de Lafayette instead, Lee agreed to fight.
Lee's troops caught up to the British column at the Monmouth court house, and attacked. The day was hot - more than 100 Fahrenheit - and soldiers on both sides dropped from heat exhaustion. Despite the weather, the Continental Army was doing well until Lee mysteriously ordered a retreat - a move that still confuses modern historians. People must have thought he was quite the pacifist for such a warrior. Though of course, people didn't know what you and I know now - it's nice to feel clever, isn't it?
First time for you?
Anyway, Lee's plan backfired - Washington arrived to find his troops retreating, but rallied them and attacked again. The two armies fought until nightfall, when the British sneaked away under cover of darkness - leaving the Continental Army victorious, but the British Army well on its way to New York. Still, it was proof that Washington's troops were - finally - a match for the British.
The battle secured Washington's reputation - and destroyed Lee's. He was arrested, court-martialed, and kicked out of the army entirely.