Previously we've seen AlphaDog, Darpa's four-legged, autonomous robot wander the woods and play fetch. Now the Pentagon's robo-beast, designed to haul supplies in rough terrain, has become smart enough to follow troops around like a loyal pet.

In the video above, released on Monday by Darpa, the AlphaDog – known as the LS3 or Legged Squad Support System – climbs rocks and trots after a soldier through wooded terrain. "We have been conducting tests to check out its mobility, perception and autonomy, and human-machine interaction," Lt. Col. Joe Hitt, Darpa's program manager, tells Danger Room. And a lot of what the robot is doing looks familiar. The machine, designed by Boston Dynamics, can stand upright, walk for 20 miles without a break and carry up to 400 pounds.

But this test has one important difference. Now the 'bot can obey instructions to follow people. The Marines connected the robot to the Marine Corps Tactical Robot Controller (TRC), a 10-pound touchscreen device a soldier or Marine can use to send the robot orders. That could be telling the AlphaDog to follow an infantry squad, or give a human operator the ability to take direct control if the 'bot hits a rough patch. The 'bot can also be given different "modes." It can follow "tight" or in a corridor, and – in the future – automatically travel to waypoints. "The robot can also provide its status through the TRC to the human operator," Hitt says.

Darpa carried out a similar demonstration on Monday for Marine Corps Commandant Gen. James Amos and Darpa director Arati Prabhakar. The 'bot moved its legs, showed off its new robot controller and tested its perception, according to a Darpa press release.

But even freakier, the Marines want to eventually hook the robot up to their radios, which could make the 'bot become responsive to verbal commands. Not only that, it could give the LS3 the ability to talk back. "We want the operator to be able to command it to come here, sit, stay. Likewise, the robot would be able to tell the operator OK, I'm stuck, I'm here, wait," Hitt says.

The robot has also become a lot quieter – 10 times quieter – since its last big test in January, according to Hitt. And that makes it 20 times quieter than when its buzzing and noisy predecessor, the BigDog, was created seven years ago. Darpa and the Marines also want to make the robot faster. During the January test, the 'bot was able to move between one and five miles per hour and managed to make it up a steep hill. The next step is doubling the speed to between seven and 10 miles per hour – allowing it to keep up with troops on the move.

It's not quite ready for combat, but the next step comes in December, when the Marines are to embed the 'bot in a series of field exercises on military bases, including in Virginia and the California desert, to last the next two years. "Imagine a mule with the smarts of a trained animal," Hitt said. But in combat, a pack animal can get scared. This pet never does.