The great armies, accumulated to provide security and preserve the peace, carried the nations to war by their own weight.
Lenin was the first to discover that capitalism 'inevitably' caused war; and he discovered this only when the First World War was already being fought. Of course he was right. Since every great state was capitalist in 1914.
In my opinion, most of the great men of the past were only there for the beer - the wealth, prestige and grandeur that went with the power.
No war is inevitable until it breaks out.
Like most of those who study history, he (Napoleon III) learned from the mistakes of the past how to make new ones.