More than 1.4 million Americans serve in the military, with about 200,000 of those troops serving overseas. Members of the armed forces can feel isolated while deployed, often in dangerous conditions. The military discovered long ago that mail boosts the morale of troops serving in other parts of the world, so it has made military mail a high priority. Military mail provides members of the armed forces with a vital link to their communities. As the “Mail Call” exhibit on military mail at the Smithsonian’s National Postal Museum notes: Mail call is the moment when the frontline and home front connect. The U.S. military mail service requires the coordinated efforts of the U.S. Postal Service and the armed forces. The current system has essentially been in place since World War II. The Postal Service is responsible for transportation of mail from U.S. postal facilities to overseas military facilities, between domestic postal facilities and air or surface carriers, while the Department of Defense manages and pays for transportation abroad and the operation of overseas military post offices. The military mail system is an extension of the domestic postal system, meaning senders of mail to Army/Air Force Post Offices (APOs) and Fleet Post Offices (FPOs) pay domestic postage rates. Over the years, the government has granted free mail services for soldiers serving in active combat sites. With the same goal of boosting morale, the U.S. Department of State, under Congress’ authorization, began establishing diplomatic post offices (DPOs) in the early 2000s. Initially, DPOs were set up for diplomats serving in hardship posts, but the State Department has since expanded the DPOs beyond such posts. Like APOs and FPOs, the Postal Service is responsible for the domestic portion of the service. The anniversary of the September 11 terrorist attacks reminds us of the importance of the armed forces and the diplomatic corps to the country’s well-being and standing in the world. The long and rich history of the military mail service is a unique, collaborative effort among parts of the government, working together to serve their public mission. For the Postal Service, military mail is an exemplary depiction of binding the nation together. To the troops and diplomats who serve overseas, it is more simply “mail call” – it is their connection to home.