How did fighting on multiple fronts (in different places) affect the countries at war?

The correct answer to this open question is the following.

Fighting on multiple fronts (in different places) affect the countries at war in that they need to invest money, soldiers, and resources in two fronts, instead of concentrating on just one and support it 100%. AS the war is fought in two separated geographical places, the military has to split strategies and supplies in those fronts and it costs a lot of money, human resources, and material resources.

For instance, during the Napoleonic wars, France fought on two or more fronts. During World War 1, Germany open two fronts in fighting Russia in the Eastern front and France, Britain, and Belgium -and later the US- in the Western front.  

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