U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. service members at Bagram Airfield, Afghanistan, Dec. 8, 2015. Dunford was traveling with USO entertainers to visit deployed service members on three continents during the holidays. DoD photo by D. Myles Cullen

Singer and songwriter Billy Montana has lunch with a U.S. Marine during a visit by the 2015 USO Holiday Tour to Bagram Airfield, Afghanistan, Dec. 8, 2015. USO entertainers were traveling to various locations to visit deployed service members. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. service members after a USO show on Bagram Air Base, Afghanistan, Dec. 8, 2015. Dunford is traveling with USO entertainers to visit deployed service members on three continents during the holidays. DoD photo by D. Myles Cullen

U.S. Army Gen. John Campbell, center left, commander of Resolute Support Mission and United States Forces—Afghanistan, welcomes U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, on Bagram Airfield, Afghanistan, Dec. 8, 2015. U.S. Air Force photo by Staff Sgt. Tony Coronado

Actress Elizabeth Banks entertains the troops during the USO Tour on Bagram Airfield, Afghanistan, Dec. 8, 2015. U.S. Air Force photo by Staff Sgt. Tony Coronado

Bahraini King Hamad bin Isa Al Khalifa, center, meets with U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, left, and U.S. Ambassador to Bahrain William V. Roebuck at Sakhir Palace in Bahrain, Dec. 7, 2015. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, and his wife, Ellyn Dunford, have dinner with U.S. service members stationed at Naval Support Activity Bahrain, Dec. 7, 2015. The chairman and performers with the 2015 USO Holiday Tour were visiting deployed service members and their families to express the country's gratitude for their service. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks to U.S. service members and their families before a USO show at Naval Support Activity Bahrain, Dec. 7, 2015. DoD photo by D. Myles Cullen

Comedian David Wain works the crowd at Naval Support Activity Bahrain, during a performance as part of the 2015 USO Holiday Tour, Dec. 7, 2015. DoD photo by D. Myles Cullen

Comedian Sydney Castillo performs for U.S. service members at Naval Support Activity Bahrain during a stop by the 2015 USO Holiday Tour, Dec. 7, 2015. DoD photo by D. Myles Cullen

A U.S. Marine shows a photo to U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, and his wife, Ellyn Dunford, at Naval Support Activity Bahrain, Dec. 7, 2015. DoD photo by D. Myles Cullen

U.S. Marine Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff and U.S. Ambassador to Bahrain, William V. Roebuck talk outside the King's palace in Bahrain, Dec. 7, 2015. DoD photo by D. Myles Cullen

U.S. Marine Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. sailors during his visit on Camp Lemonnier, Djibouti, Dec 6, 2015. Dunford is traveling with entertainers to visit U.S. service members overseas during the 2015 USO Holiday Tour. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, and his wife, Ellyn Dunford, talk with U.S. service members and their families after a USO show on Naval Air Station Sigonella, Italy, Dec. 5, 2015. The chairman is visiting U.S. service members deployed overseas while bringing the 2015 USO Entertainment Troupe on a holiday tour to perform for U.S. troops in Europe, Africa and Asia. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. service members and their families at the beginning of a USO show on Naval Air Station Sigonella, Italy, Dec. 5, 2015. Dunford is traveling with entertainers to visit deployed service members during the 2015 USO Holiday Tour. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. service members on Naval Air Station Sigonella, Italy, Dec. 5, 2015. Dunford is traveling with entertainers to visit deployed service members during the 2015 USO Holiday Tour. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. Marines stationed on Naval Air Station Sigonella, Italy, Dec. 5, 2015. DoD photo by D. Myles Cullen

U.S. Marine Corps Gen. Joseph F. Dunford Jr., chairman of the Joint Chiefs of Staff, talks with U.S. airmen on Naval Air Station Sigonella, Italy, Dec. 5, 2015. DoD photo by D. Myles Cullen