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Let us assume that, for whatever reason, the Nationalists haven't managed to decisively vanquish the Republicans by the time Germany invades Poland and WW2 begins. Let's say, for example, that the Battle of Teruel goes better for the Republicans, who don't exhaust their manpower and resources fighting it, so that the Nationalists are unable to proceed to the Aragon offensive on schedule (though any military POD experts on the Spanish War can think of may do as well).

All other things being equal, what would be the strategic consequences of the Spanish War still raging by the time Britain and France declare war on Germany? (Or would Germany delay the invasion of Poland to begin with?) It seems likely that the Republicans would seize the opportunity to declare war on Germany as well, in order to formally become co-belligerent of the Allies, and as such receive desperately-needed support. What would be the butterflies of such a development?
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