Why Sweden did not enter the Norwegian campaign

Why did Sweden stay out when Germany invaded Norway?

Sweden had no assurance of outside support, Norway did not ask it to enter, the two countries carried historical baggage, and economic interests also favored caution.

Sweden had just watched Norway fall without evidence that intervention would bring reliable Allied support. Norway did not request Swedish entry, and the relationship carried memories of earlier Swedish rule. Economic considerations added another reason not to begin a war with Germany. These constraints explain why an intervention that could hurt Germany was still politically unlikely.