WASHINGTON -- Upholding the Constitution of the United States can require sacrifices that may be understood only by those who have sworn an oath to defend it, said the Army's top uniformed leader during a ceremony Sunday on Bagram Air Base, Afghanistan.

"Just last month five Americans were killed here at Bagram fulfilling that oath," Gen. Mark Milley said.

Milley and Sgt. Maj. of the Army Daniel Dailey ushered in the holidays, visiting Soldiers, commanders and government officials in Afghanistan, Iraq, Jordan and Israel Dec. 16 to 22.

In Afghanistan, Milley reenlisted several Soldiers from the 1st Cavalry and 1st Infantry divisions and spoke of the importance of the oath of office and the constitutional guarantee of freedom to all Americans, regardless of race, religion or gender. He told the Soldiers that he had come to thank them personally for their service

"I find it helpful to remind myself why we're here in Afghanistan when it can seem like Groundhog's Day if you've been deployed here multiple times," he said. "Never forget that the people who attacked America, who hate that freedom you swore an oath to die if necessary to defend, planned their attacks right here in this country. You are here to help ensure that will never, ever happen again."

Also in Afghanistan, Milley met with Gen. John Nicholson, the commander of the NATO Resolute Support mission, as well as multiple U.S. military commanders from U.S. Forces-Afghanistan and senior Afghan government leaders.

While in the country, Milley also discussed the ongoing assistance U.S. forces are providing to the Afghan Army and police forces with Gen. Qadam Shah Shahim, chief of the general staff of Afghan National Army, and Abdullah Habibi, Afghanistan's Defense Minister.

During the Iraq portion of their trip, Milley met with commanders from Combined Joint Task Force-Operation Inherent Resolve who are advising and assisting the Iraqi Security Forces to retake Mosul from ISIL.

Milley also met with Iraqi Staff Lt. Gen. Abdul Amir Yarallah, the Iraqi Army's deputy chief of staff for operations and Karim Sinjari, the Kurdistan Regional Government's minister of Peshmerga.

Milley praised both the Iraqis and the Kurds for their efforts on working together to defeat ISIL and congratulated them on the progress made so far to retake eastern portions of the city.

Dailey held a series of town hall meetings with troops in Afghanistan and Iraq, during which he discussed current issues in the Army. Included among the topics were the STEP program -- which stands for select, train, educate, promote -- changes to the Army's promotion system, Soldiers' roles and responsibilities to achieve the Army's readiness priority, and the high quality of Soldiers joining the Army.

"I was at basic training recently and went for a four-mile run at a seven-minute pace and not one of these new recruits fell out of formation," Dailey said, emphasizing one aspect of standards new recruits are required to meet in basic training.

He also spoke about the Army's historic level of female enlistees. Dailey noted that in 2016 the Army achieved a 10-year high for the number of women enlisting. Two hundred of the more than 14,000 new female recruits enlisted for combat arms specialties, he said, exceeding the Army's own estimates of the number of women who would be interested in joining the newly opened combat arms branch.

Milley and Dailey continued their trip with a stop in the Hashemite Kingdom of Jordan, where they met with Soldiers who are training alongside the Jordan Armed Forces-Arab Army. Milley met with King Abdullah, Prince Faisal and Lt. Gen. Mahmoud Freihat, Jordan's chairman of the Joint Chiefs of Staff. Milley thanked them for Jordan's participation as a leading member of the counter-ISIL coalition.

Milley concluded his trip in Israel, where he met with Lt. Gen. Gadi Eizenkot, the chief of the general staff of the Israel Defense Forces, and Maj. Gen. Kobi Barak, the ground forces commander, and reaffirmed the U.S. commitment to the bilateral security alliance.

Currently, more than 180,000 Soldiers are deployed to 140 countries around the world in a variety of missions, including deterrence, reassuring allies and partners, advising and assisting foreign militaries, counter-insurgency and counter-terrorism operations, and military partnership training.