For definition of world war will say fighting on every continent exception of Australia and Antarctica. First there is North and South America which haven't had major war fought on them for over century. Europe is generally united under German sphere. Africa would never be somewhere world war start due to lack of major foreign allies. Russia is backwater, and economy is in shambles after Crimean occupation. China is prosperous and expanding sphere through peaceful investment, in good time Chinese economy shall sore past United States economy.
