Today's dismounted warfighter can be saddled with more than 100 pounds of gear, resulting in physical strain, fatigue, and degraded performance. To help alleviate the impact of excess weight on troops, DARPA is developing a highly mobile, semi-autonomous four-legged robot, the Legged Squad Support System (LS3). LS3 includes onboard sensors to perceive obstacles in its environment and path-planning capabilities to avoid them. The LS3 platform is designed with the squad in mind and is therefore significantly quieter, faster and has a much higher carrying capacity for longer mission durations than DARPA's earlier mobility technology demonstrator BigDog. The LS3 prototype recently completed its first outdoor assessment, demonstrating mobility by climbing and descending a hill and exercising its perception and autonomous follow-the-leader capabilities.