Comment by crote

It wasn't wrong, just too early.

At the time international trade was still fairly minor, so although a war would be deeply unprofitable it'd still be possible. Today's economy looks quite different, with even basic consumer goods coming from overseas. If international trade were to suddenly cease, most major countries would be in serious trouble really quickly.

The most extreme example of this is the European Union. Its economies are so deeply interwoven that they act as a single entity. Separating them to the point that one of its members can independently support a war economy would take decades, so it does indeed make intra-European wars virtually impossible.