Perhaps you are thinking of George Armstrong Custer, a famed but controversial cavalry general who served under Grant's command during the Civil War. Custer was known for his bravado and bold tactics, but he also suffered a tragic defeat at the Battle of Little Bighorn.
It is important to be clear about who you are asking about to get the correct information. If you are interested in learning more about Grant or Custer, let me know and I can provide you with more details about their careers.