When it comes to understanding what it means to be an American, few people have a better grasp of the concept  than retired Marine Gen. John F. Kelly, set to become the secretary of Homeland Security in the Trump Administration. Not only did Kelly spend more than 40 years of his life in uniform, serving in both Desert Storm and the initial invasion of Iraq alongside Gen. James F. Mattis, he’s a Gold Star father. In 2010, Kelly’s son, Robert, was killed in action as a Marine serving in Afghanistan.