Military strategies will shortly make intensive use of autonomous systems while the Internet of Battle Things (IoBT) will grow military systems' complexity to new heights. The cyber defense of the battlespace will then become arduous for humans, if not impossible, due to disconnections, the difficulty of supervising masses of interconnected devices, and the scarcity of cyber defense competences on the battleground. An autonomous intelligent cyber defense of the battlefield becomes necessary in such a context. In response to such needs, this chapter presents and illustrates the rationale, concept and future research directions of (Multiple) Autonomous Intelligent Cyber defense Agents, (M)AICA, and NATO's initial AICA Reference Architecture, AICARA.