The Tank Urban Survival Kit (TUSK) is a series of improvements to the M1 Abrams intended to improve fighting ability in urban environments. Historically, urban and other close battlefields have been poor places for tanks to fight. A tank's front armor is much stronger than that on the sides, top, or rear. In an urban environment, attacks can come from any direction, and attackers can get close enough to reliably hit weak points in the tank's armor or gain sufficient elevation to hit the top armor. Armor upgrades include reactive armor on the sides of the tank and slat armor (similar to that on the Stryker) on the rear to protect against rocket-propelled grenades and other shaped charge warheads. A Transparent Armor Gun Shield and a thermal sight system are added to the loader's top-mounted M240B 7.62 mm machine gun, and a Kongsberg Gruppen Remote Weapon Turret carrying a 12.7 mm (.50 in) caliber machine gun (again similar to that used on the Stryker) is in place of the tank commander's original 12.7 mm (.50 in) caliber machine gun mount, wherein the commander had to expose himself to fire the weapon manually. An exterior telephone allows supporting infantry to communicate with the tank commander. General Dynamics M1A2 Abrams TUSK General Dynamics delivered the first M1 Abrams to the U.S. Army in 1980. The Abrams is a full tracked, low profile land combat system possessing a high degree of armor protection, lethal firepower, maneuverability and agility. It is built primarily from sturdy rolled homogeneous armor steel plates, sandwiched around thicker protective material. Its four man crew is aided by an array of sensors that constantly monitor the tank's tilt, the turret's motion and any gusts of wind; a computer adjusts the gun accordingly to keep it aimed at its target. With this system, the M1 can take out other tanks while on the move.