Is commerce rendering war obsolete?

In his essay “To Perpetual Peace: A Philosophical Sketch,” Kant wrote that “the spirit of commerce, which is incompatible with war, sooner or later gains the upper hand in every state.”

Kant was not a friend of the spirit of commerce, which he associated with the Jews, whom he despised as “immoral and vile” and as a “nation of swindlers.” Nonetheless he believed that the spirit of commerce is opposed the spirit of war.

John Stuart Mill agreed: “It is commerce which is rapidly rendering war obsolete.”

Unlike Kant, Mill was fully in favor of this development: “commerce first taught nations to see with good will the wealth and prosperity of one another,” which overcomes the tradition of seeing other countries’ gains as your country’s losses, which leads to a lessening of war and an increase in mutually-beneficial interactions. That’s from Mill’s Principles of Political Economy, Book III, Chapter XVII, Section 14.

Kant and Mill are asserting the “Capitalist Peace” thesis, which is related to the “Democratic Peace” thesis, both of which can be integrated to form a “Liberal Peace” thesis.

For a recent version of democratic peace, I recommend the University of Hawaii’s Rudolph Rummel’s Power Kills: Democracy as a Method of Nonviolence (Transaction Publishers, 1997), and for a contemporary version of capitalist peace, I recommend Columbia University’s Eric Gartzke’s essay “The Capitalist Peace” [pdf].

Some questions for the capitalist peace thesis:

* The relatively peaceful nineteenth century was friendly to the capitalist peace thesis. True?
* The relatively war-ful twentieth century—does it undermine the capitalist peace thesis?
* Wars in the twentieth century were capitalist-leaning countries fighting socialist countries. True?
* Are there any twentieth-century examples of capitalist-leaning countries fighting wars against other capitalist-leaning countries?