Question: What is the narionality of the author of the biography Halleck: Lincoln's Chief of Staff ?
Context: Halleck: Lincoln's Chief of Staff is the biography of Union Army General-in-Chief Henry Halleck written by Stephen E. Ambrose and published in 1962.  In this book, Ambrose provides an interpretation contrary to previous assessments of this "controversial figure" from the American Civil War. John Rodgers Meigs (February 9, 1842 – October 3, 1864) was an officer in the Union Army during the American Civil War.  He was the son of Brigadier General Montgomery C. Meigs, the Quartermaster General of the United States Army.  He participated in the First Battle of Bull Run, and later testified in the court-martial trial of an officer involved in the retreat from the battle.  He attended the United States Military Academy, where he was an acting assistant professor of mathematics and graduated first in his class in June 1863.  He was lauded by Secretary of War Edwin M. Stanton for strengthening the defenses of Baltimore, Maryland; was an engineer and acting aide-de-camp on the staff of Brigadier General (Volunteers) William W. Averell; was Chief Engineer of the Shenandoah Valley for the Department of West Virginia; and was Chief Engineer of the Middle Military Division and aide-de-camp to General Phillip Sheridan.  The circumstances under which Meigs died led to the burning of Dayton, Virginia, in retaliation.  His funeral was a public event attended by President Abraham Lincoln, Stanton, and numerous government dignitaries.  A book of Meigs' letters were published in 2006 under the title "A Civil War Soldier of Christ and Country: The Selected Correspondence of John Rodgers Meigs, 1859-64". Vice Admiral Sir Neil Dudley Anderson, {'1': ", '2': ", '3': ", '4': "} (5 April 1927 – 5 June 2010) was a senior officer in the Royal New Zealand Navy whose career culminated with his appointment as Chief of Naval Staff from 1978 to 1980, and then Chief of Defence Staff from 1980 to 1983.  He was married to the author Barbara Anderson.  He died on 5 June 2010 aged 83. Philip Gefter is an American author and photography critic.  He wrote the biography of Sam Wagstaff, "Wagstaff: Before and After Mapplethorpe", for which he received the 2014 Marfield Prize, the national award for arts writing.  He is also the author of "George Dureau: The Photographs", and "Photography After Frank", a book of essays published by "Aperture" in 2009.  He was on staff at "The New York Times" for over fifteen years, where he wrote regularly about photography.  He produced the 2011 documentary film, "Bill Cunningham New York". Leonard Wong is a Research Professor of Military Strategy (Human and Organizational Dimensions) in the Strategic Studies Institute at the U.S. Army War College, who focuses on the human and organizational dimensions of the military, and is a published author on leadership strategy.  Wong is a registered professional engineer and holds a Bachelor of Science from the United States Military Academy, and an M.S.B.A. and Ph.D. from Texas Tech University.  His 1992 thesis was on "The effects of cohesion on organizational performance: a test of two models" using performance data of unit battles at the U.S. Army's National Training Center, Fort Irwin, California.  He joined the Strategic Studies Institute in July 2000 after serving 20 years in the United States Army, reaching the rank of lieutenant colonel.  His army career included assignments teaching leadership at West Point, serving as an analyst in the Office of the Chief of Staff of the United States Army and in the Office of the Deputy Chief of Staff for Personnel, and serving as the Director of the Office of Economic and Manpower Analysis (OEMA).  He has authored several articles, chapters, and papers on organizational issues in the Army such as downsizing, leadership, junior officer retention, professionalism, and innovation in the military. Zhao Jingyi (趙敬怡) (d. March 24, 929) was a general of the Chinese Five Dynasties and Ten Kingdoms Period state Later Tang, serving as one of emperor's chiefs of staff ("Shumishi") from 928 to 929.  Prior to serving as chief of staff, he was the deputy military governor of Tianxiong Circuit (天雄, headquartered in modern Handan, Hebei).  He died in office as "Shumishi".  As there was no biography for him in the "Old History of the Five Dynasties" or the "New History of the Five Dynasties", there is otherwise no extant record of his career. Robert Lewis Dabney (March 5, 1820 – January 3, 1898) was an American Christian theologian, Southern Presbyterian pastor, Confederate States Army chaplain, and architect.  He was also chief of staff and biographer to Stonewall Jackson.  His biography of Jackson remains in print today. David Henderson (born 1927) is a British economist.  He was the chief economist at the Economics and Statistics Department at the OECD in 1984–1992.  Before that he worked as an academic economist in Britain, first at Oxford (Fellow of Lincoln College) and later at University College London (Professor of Economics, 1975–1983); as a British civil servant (first as an Economic Advisor in HM Treasury, and later as Chief Economist in the Ministry of Aviation); and as a staff member of the World Bank (1969–1975).  In 1985 he gave the BBC Reith Lectures, which were published in the book "Innocence and Design: The Influence of Economic Ideas on Policy" (Blackwell, 1986). The Monk Who Became Chief Minister is a biography of Yogi Adityanath, the 21st Chief Minister of Uttar Pradesh.  It is written by Shantanu Gupta, an Indian Author and Political Analyst.  The book has been published by Bloomsbury Publishing, India and came out on August 25, 2017.  The cover of the biography was released on 23 July 2017 at an event of CREDAI at Lucknow. Stephen Edward Ambrose (January 10, 1936 – October 13, 2002) was an American historian and biographer of U.S. Presidents Dwight D. Eisenhower and Richard Nixon.  He was a longtime professor of history at the University of New Orleans and the author of many bestselling volumes of American popular history.
Answer: American