This is woeful selective reading of history. Warfare was a constant everywhere in the world before the industrial revolution. Also 19th century Europe (since Napoleon's fall to WWI) was largely free of war.
Well, if you exclude (and these categories are overlapping and non-exhaustive) the Italian wars of independence, conflicts associated with the 1848 revolutions, the various wars involving Russia and it's neighbors, the wars between the Ottoman Empire and it's breakaway regions, the wars between regions that has broken away from the Ottoman Empire, the (with substantial outside intervention) Portuguese Civil War, the Franco-Prussian War, the (again, with substantial outside intervention) series of civil wars in Spain, the Schleswig Wars, and the wars of German Unification...Sure, maybe the post-Napoleon I 19th Century was relatively free from war in Europe.
If you don't ignore those, war was pretty much constant in the period.