The D7 series medium bulldozer began service with the U.S. military during World War II. With upgrades and changes, it has been a workhorse for the U.S. military, fulfilling its primary earthmoving role as well as a host of other roles discovered for it, for example mine clearing with a special flail adapter kit. Its latest version, the D7R is currently used by the U.S. Army, being the primary earthmover for construction of survivability positions and antitank ditches. It must be transported by trailer due to its poor mobility.