Background: Brad Rogers Carson (born March 11, 1967) is an American lawyer and politician from the state of Oklahoma who served as the Acting Under Secretary of Defense for Personnel and Readiness from 2015-16. In that role, he initiated a number of notable reforms to include opening up all combat positions to women, open service by transgender service members, and new recruiting and retention practices. A member of the Democratic Party, he served in the United States House of Representatives from 2001-05. He served as Undersecretary of the Army from 2014-15 and as General Counsel of the Army from 2012-2014.
Context: After the 2004 Senate election, Carson's term in the United States Congress expired on January 3, 2005; Carson was succeeded by Dan Boren. Carson indicated that he had no immediate plans to seek political office, and, in January 2005, he accepted a semester-long teaching fellowship specializing in U.S. politics at Harvard University. Upon leaving Harvard, he returned to his hometown of Claremore, Oklahoma, and worked as Chief Executive Officer of Cherokee Nation Businesses, which is owned by the Cherokee Nation of Oklahoma in Catoosa, Oklahoma.  As an expert in Indian law, Carson oversaw one of the largest businesses in the state, with thousands of employees, hundreds of millions of dollars in revenue, and more than a dozen in-house lawyers who specialized in Indian and corporate law. In December 2008, Carson left his post at Cherokee Nation Businesses to deploy to Iraq as an Intelligence Officer in the U.S. Navy. He was officer-in-charge of weapons intelligence teams embedded with the U.S. Army's 84th Explosive Ordnance Disposal Battalion in the nine southern provinces of Iraq; the teams worked with EOD teams at seven bases and investigated bomb sites, caches, smuggling routes, and other activities related to improvised explosive devices. For this work, Carson received, among other awards, the Bronze Star. On his return, he was elected to the board of Cherokee Nation Businesses.  In January 2010, Carson assumed a position as professor of business and law and at the University of Tulsa and as director of the National Energy Policy Institute, a non-profit energy policy organization funded by billionaire George Kaiser's family foundation. In his academic work, Carson has written extensively about the economics of renewable energy. He has also contributed journalism to The Weekly Standard, The New Republic, Blueprint, and Democracy: A Journal of Ideas. In 2010, Carson contributed to a symposium issue of Democracy: A Journal of Ideas, in which he was one of ten writers (including Martha Nussbaum, Michael Sandel, and others) discussing the future of progressive political thought and politics. He is the author of several other works, including a guide to federal appellate practice, a work co-authored with Judge Robert Bacharach (who was appointed by President Obama to the 10th Circuit Court of Appeals). More recently, he has been working on a long series of articles about military reform for the online journal War on the Rocks.  Carson had met Barack Obama in 2004 when they were both nominees of the Democratic Party for open seats in the United States Senate. Carson endorsed Obama in 2006 for the 2008 presidential election. Carson served as Obama's personal representative in the approval of candidates for delegates from Oklahoma to the 2008 Democratic National Convention. Oklahoma was the first state to name its complete delegation to the 2008 Democratic Convention.  Carson's wife, Julie, served on the Oklahoma State Regents for Higher Education. They live in Claremore, Oklahoma. They have one son, Jack.
Question: What did he do after he left Congress?

Answer:
he accepted a semester-long teaching fellowship specializing in U.S. politics at Harvard University.