While previous research on foreign recruitment has investigated how rebels manage to recruit from abroad, little attention has been given to the factors that regulate demand from the rebel point of view. This thesis suggests that the organizational complexity of a rebel group affects its range of personnel needs and capability of rendering recruits into military assets. By conducting a comparative case analysis of Al Qaeda in Iraq (2004-2008) and The Islamic State (2012-2016), the study finds that the variety in foreign recruits experienced by the groups in part can be explained by varying degrees of demand. While organizational complexity cannot be established as determiner for the theoretically suggested mechanisms, it does appear to be a strong predictor for both the needs and capabilities of rebels who recruit from abroad.