Every war has its winners and losers, but countries have nothing to do with it. The ruling class inevitably makes a tidy profit from war, while the working class loses its flesh and blood on the front-line.
Workers' solidarity does not recognise national boundaries, but instead unites against a common class enemy. The surest way to stop a war is by refusing to participate in it, which is why the IWW believes that it is important to educate workers in the armed forces and so-called defense industries about where their true self-interest lies.