I was just reading A.fm.'s comment on this question.
[...] and history shows democratic states don't fight one another.
At first I thought this statement was wrong, but thinking further I couldn't find any example of two unquestionably democratic states engagint a war with eachother. I can only find examples of democracy declaring war to a dictatorship (USA invading Irak in 2003) or a dictatorship invading a democracy (for example Germany invading Czechoslovakia in 1938). Cases of two dictatorship attacking eachother are unfortunately too common so that no example is needed...
The best counter-example to A.fm.'s claim I can find is Austria-Hungary declaring war to Serbia in 1914... but both of those countries were more hybrid regimes than full democraties it seems.
France declaring war to Prussia in 1870 is also borderline making it, but both countries were kind of hybrid/half-democraties at this point of time.