The paper shows how the semantically underspecified imperfective aspect in Russian becomes associated with counterfactual complete events in specific contexts, notably in chess annotations (Restan 1989), while the perfective invariably denotes factual complete events. The counterfactual flavour of the construction invites a comparison with more standard counterfactual conditionals, including some discussion of the imperfective and counterfactuality in French. I show that the “counterfactual imperfective” in Russian differs from ordinary counterfactual conditionals, which are characterized by a semantically empty past tense. This subtle distinction leads to a further division of pragmatic labour between the form “imperfective past” (hypotheses in the past) and the “subjunctive (“by”) perfective past” (hypotheses in the present/future). The analysis is couched in Bidirectional Optimality Theory (Blutner 2000), which provides an ideal framework for analyzing non-compositional form-meaning optimization and pragmatic strengthening.