US Marines position their rigid-hull inflatable boat to conduct a visit, board, search and seizure (VBSS) mission as part of an exercise on the Gulf of Aden in the Middle East on Saturday, December 17. Gunnery Sgt. Robert B. Brown /U.S. Marine Corps

Staff Sgt. Ryan Molina scales a wall while completing an obstacle course at the Marine Corps Base Hawaii naval station on Thursday, December 15. Molina was taking part in a Martial Arts Instructor Course (MAIC), a rigorous three-week exercise designed to instill teamwork and develop leadership abilities. Sgt. Brittney Vella/U.S. Marine Corps

US Marines fire an FGM-148 Javelin missile during an exercise at the Novo Selo Training Area in Bulgaria on Thursday, December 15. The live-fire exercise aimed to strengthen security and regional defenses in Eastern Europe. Sgt. Michelle ReifU.S. Marine Corps

US Air Force Staff Sgt. Jamie Matheney refuels a United Arab Emirates F-16 Desert Falcon jet during a mission over Iraq on Friday, December 9. The KC-135 Stratotanker provides aerial refueling capabilities and supports Iraqi security forces and partners in Syria as they work to liberate territory and people under the control of ISIS. Staff Sgt. Matthew Fredericks/U.S. Air Force

Actress Scarlett Johansson, second from right, smiles during a visit to the US Air Force's 39th Air Base Wing in Adana, Turkey, on Wednesday, December 7. With her were actor Chris Evans, former NBA player Ray Allen, singer Craig Campbell and American swimmer Maya DiRado. Incirlik Air Base/Anadolu Agency/Getty Images

US Marine honor guards stand by former astronaut and US Sen. John Glenn lying in repose at the Ohio Statehouse in Columbus, Ohio, on Friday, December 16. Glenn, the first American to orbit the Earth, died at the age of 95 on December 8. Bill Ingalls/NASA

Wesley Clark Jr. kneels in front of Leonard Crow Dog during a forgiveness ceremony at the Standing Rock Sioux Reservation in Fort Yates, North Dakota, on Monday, December 5. A group of US veterans asked Native Americans to forgive the military actions carried out against Native American people throughout history. Helen H. Richardson/Denver Post/Getty Images

The EchoStar 19 spacecraft launches from aboard an Atlas V rocket in Cape Canaveral, Florida, on Sunday, December 18. The launch was supported by the US Air Force's 45th Space Wing unit. Jeff Spotts/ULA

USS Arizona survivor Louis Conter poses for a photograph before the start of a ceremony commemorating the 75th anniversary of the attack on Pearl Harbor in Honolulu, Hawaii, on Wednesday, December 7. The USS Arizona was sunk in 1941 when the Japanese Imperial Navy launched a surprise attack on the US naval base. More than 2,000 Americans were killed in the bombings, which destroyed a significant number of US battleships and airplanes. Kent Nishimura/Getty Images

Army cadets toss the head of Navy's "Bill the Goat" mascot during a football game between the Army Black Nights and the Navy Midshipmen on Saturday, December 10. Army won, 21-17. Baltimore Sun/Tribune News Service/Getty Images

US military personnel recover the wreckage of an MV-22 Osprey aircraft on the coast of Nago, Japan, on Thursday, December 15, after it crash-landed two days earlier. Kyodo News/Getty Images

US Marines operate amphibious assault vehicles (AAV) during an exercise on Tuesday, December 6. The exercise involved the Makin Island Amphibious Ready Group and helped the 11th Marine Expeditionary Unit prepare for crisis response and contingency operations. Lance Cpl. Devan Gowans/U.S. Marine Corps

Family members of US Air Force Maj. Troy Gilbert place roses on his casket during his final interment at Arlington National Cemetery in Arlington, Virginia, on Monday, December 19. Gilbert was killed while on a mission on November 27, 2006, when his F-16C Fighting Falcon crashed approximately 20 miles northwest of Baghdad, Iraq. According to the US Air Force , most of Gilbert's remains had been missing in Iraq for nearly a decade until October 2016. Tech. Sgt. Joshua DeMotts/U.S. Air Force

The US Navy's USS Zumwalt (DDG 1000) steams in formation with USS Independence (LCS 2) and USS Bunker Hill (CG 52) somewhere in the Pacific Ocean on Thursday, December 8. The USS Zumwalt was on the final leg of her three-month journey to her new home port in San Diego and is the Navy's most technologically advanced surface ship. Petty Officer 1st Class Ace Rheaume/U.S. Navy

A veteran pens his signature on a QF-4 Phantom during a "Pet the Jet" portion of the Phinal Phlight commemoration at Holloman Air Force Base in New Mexico on Wednesday, December 21. To date, the QF-4 Phantom has flown approximately 145 unmanned sorties. Staff Sgt. Eboni Prince/U.S. Air Force

The crew of the US Coast Guard ship Hamilton use a crane to offload approximately 26.5 tons of cocaine in Fort Lauderdale, Florida, on Thursday, December 15. The drugs, worth an estimated $715 million, were from 27 separate suspected drug smuggling vessels and 5 bale recovery operations by the US Coast Guard, Royal Canadian Navy and its interagency partners. Joe Raedle/Getty Images