The Sentry Drone is the United States' detector unit and unmanned sentry, armed with a high calibre gatling gun and equipped with top of the line sensors.
The Sentry Drone comes from a long line of failed prototypes. Billions of dollars were pumped into the development of the perfect scout. The first prototypes produced used to be as expensive as a tank and used to break down often. The second line were cheaper, however they had to be remote controlled by somebody within a hundred miles. The third and final version was cheaper, was capable of accomplishing its mission even without supervision and could operate for over a week without maintenance. Decades have passed, and the model we see today is a distant cousin of the first crude unmanned ground vehicles fielded after the turn of the millennium. The Rottweiler Sentry Drone has been a workhorse of the United States military since the Global War on Terror and has been given another systems upgrade to keep up with the times. Recent problems with manufacturing Sentry Drones in bulk have resulted in them no longer being able to stealth themselves.