How did imperialism set the stage for both world wars?

Imperialism was a cause for both WWI and WWII. Imperialism is a broad policy in which a country tries to extend its power or influence, often by gaining territory. This can be done for national prestige, security, or economic reasons.  The modern nation of Germany was founded in 1871, and by then there were few other places to colonize.  Germany gained some land in Africa and a few islands in the Pacific, but that is...

Imperialism was a cause for both WWI and WWII. Imperialism is a broad policy in which a country tries to extend its power or influence, often by gaining territory. This can be done for national prestige, security, or economic reasons.  The modern nation of Germany was founded in 1871, and by then there were few other places to colonize.  Germany gained some land in Africa and a few islands in the Pacific, but that is all that was available since the rest of Europe had already colonized most of the developing world.  Germany built up its armed forces, particularly its navy, to gain and maintain control of its overseas possessions.  This alarmed Britain, the leading naval superpower in the world, into enlarging its battleship fleet, thus creating an arms race and increasing militarism in both countries.  Also, Britain, France, and Russia looked on with interest as the Ottoman Empire slowly collapsed and each nation plotted how it would gain new territory in the Middle East.  

WWII was launched by imperialism.  Hitler convinced the German people that the only way to international respect and power was to create a greater Germany, which he achieved by annexing Austria and Czechoslovakia.  He then invaded Poland and the Low Countries.  His greatest and most costly land grab was when he invaded the Soviet Union in order to secure "living space" for German settlers.  Japan felt cheated at the Treaty of Versailles in that it had to give up a lot of the territory it grabbed in WWI.  Japan sought to become the major power in the Pacific, so it invaded China, Korea, and many of the Pacific archipelagos.  Italy also felt cheated at the Versailles conference because the Allies used territorial gains to bribe it into coming into the war on their side.  Once these gains did not materialize, Benito Mussolini came to power and established what he hoped would be a new Roman Empire.  He invaded Ethiopia, Albania, and Libya.  While economics was the driving factor behind the imperialism that predated WWI, revenge was the motivation behind WWII's imperialism.