Hamilton was an interesting fellow, and while he is best known for his role in the American Constitution and government following the Revolution, he was no passive bystander in the war itself.
He was a young man, only 20, when war broke out, and though he came from humble means, he was attending college at Columbia University (then known as King's College) in New York when war broke out. He was intelligent and well spoken, but he also had guts and an uncanny ability to read a battlefield while still accurately perceiving the big picture of the war in his head. He acquitted himself well in battle on Long Island and at Trenton and Princeton during the low water mark of Washington's army.
This was when he became Washington's personal assistant. He was placed in charge of making recommendations for streamlining the American military and correcting mistakes and issues that arose, and earned Washington's respect in doing so.
A little known argument between himself and Washington in 1780 led him to resign, where he took over as a batallion commander at Yorktown in 1781. He retired from the war as a Colonel.