The document discusses the limitations of battery power for small autonomous robots and soldiers. While small robots are attractive for defense applications like reconnaissance and patrolling, battery technology cannot provide enough energy density for more than an hour or two of operation. Fuel cells and generators are not feasible options at small scales either. However, the document suggests some potential solutions being explored, such as photovoltaic energy capture from flames, novel engine/generator combinations, or single-use power sources that could operate for a day before recycling. The goal is to develop alternative power sources that would enable the widespread use of smaller autonomous robots in defense applications.