From the Boston Globe:

“As a lieutenant colonel in the Massachusetts Army National Guard, I have service obligations that I fulfill each year.
“Following in the tradition of other lawmakers who have completed their military service requirements overseas, this year I have requested to conduct my annual training in Afghanistan.
“Doing so will help me to better understand our ongoing mission in that country, and provide me first-hand experience for my duties on the Senate Armed Services, Homeland Security, and Veterans Affairs committees,” he said.