The document discusses the limitations of battery power for small autonomous robots and soldiers. While smaller robots are safer and more practical for defense applications, current battery technology only allows for an hour or two of operation, which is not enough. Batteries are also limited in their energy density and unlikely to improve much in the next 10-20 years. The document proposes potential alternative power solutions that could be explored, such as photovoltaic energy capture from flames, novel engine/generator combinations, or single-use power sources that last a day or two before recycling. It concludes that long-endurance power sources for smaller robots present an opportunity for defense applications if technical challenges can be addressed.