First, to stopping te Germans'war: They were never adequately punished for the aggression of 1914. If the victors at Versailles had occupied Germany for several decades (at German expense) to execute its war criminals and block any rearming, even a peashooter, they'd never have been able to launch another war. Fortunately the crime of aggression was taken a bit more seriously at Nuremberg and Tokyo after 1945.

Islamic State won't disappear until its vile source - Islam - is defeated by ideological war against its expansionist threat to freedom as set out loud and clear in its holy books.

However, as a threat to world peace Islamic State is puny. A far more credible threat to world peace, already armed with nukes, has (like its sister regime in South Africa) been fostered since 1947-8 in Palestine. For an idea of how immediate a threat it is, read its own words at http://www.meforum.org/5385/israel-iran-nuclear-buildup (and note that the Great Powers are at last starting to turn against it).