We instantly see that the old saying "Democratic nations don't start wars" is entirely wrong for a number of reasons and that we have to differ between the ages of democratic nations.
But wait, his article holds so much more, here.
This paradox has made minor celebrities out of a pair of political-science professors, who came out with the right book at the right time (Electing to Fight; for a summary click here). Jack Mansfield and Ed Snyder distinguish between "mature democracies", which never, never start wars ("hardly ever", as the captain of the Pinafore sang), and "emerging democracies", which start them all the time, in fact far more frequently than do dictatorships.
I especially want to go on this point, which is fairly interesting and I think I have an reasonable explanation (read BOCTAOE here). Of course, a democracy has a lot of incentive to wage war abroad, because the war at home it has already won. If you are a leading party in a democracy, you have the will of the people already behind you, while as an dictator you have to fight for every inch of it on any given day (as long as you have a head and stay in power).
A dictator has a dreadful daily routine of having to secure his own throne and looking out for possible opponents, always instructing the secret police to make examples of possible traitors day in and out. With such a tight schedule you don't have time to wage war on other countries (except you need some PR like Saddam in his little Iranian adventure).
I'd also like to say that "mature" dictatorships are less a threat than mature democracies. If we look at Cuba, North Korea amongst others, we see that they seldom or never attack other countries any more, most unlike to the USA. Perhaps this is also dependent on size, but if we look at Iraq, then we see that Saddam started a war against Kuwait not long ago.
So, I accept that this statement is not necessarily true, because you have to state what is a mature/immature dictatorship.
But still, in the median I believe that dictatorships are not waging any more wars than any democracy(BOCTAOE). However, this of course does not say that it is nice to live in a dictatorship or to have many such political societies (YSLE!!!). Instead I think it is a fact that can start to engage the self-righteousness of "DEMOCRACY" as the end of political evolution and the utter most best thing for human beings to achieve!