What would the religious map of Europe look like today if the English Civil War had taken place a decade earlier, putting well-disciplined English troops into the field on the Protestant side of the Thirty Years’ War?
Update The expert consensus seems to be that the result would have been about the same, because England wouldn’t have come in or wouldn’t have been effective, or maybe weirdly different if England had come in against Holland and/or France or if its entry on the Protestant side had caused France to switch sides or get out, but in any case probably not a net gain for the anti-Habsburg cause.