We extend the epistemic analysis of dynamic games of Battigalli and Siniscalchi (1999, 2002, 2007 from …nite dynamic games to all simple games, that is, …nite and in…nite-horizon games with …nite action sets at non-terminal stages and compact action sets at terminal stages. We prove a generalization of Lubin's (1974) extension result to deal with conditional probability systems and strong belief. With this, we can provide a short proof of the following result: in every simple dynamic game, strong rationalizability characterizes the behavioral implications of rationality and common strong belief in rationality.