Lenin faced huge economic challenges after the Russian civil war - primarily economic ones. War communism was ineffective in salvaging the Russian economy, such a failure was the first insight into the way in which the communist ideology conflicts with the human condition. Because of the lack of recovery, Lenin introduced the New Economic Policy (NEP) which included certain capitalist element in hopes of reviving the economy. However, Lenin was aware that the NEP had to be a temporary element if Russia was to be truly communist. Lenin was now faced with the tasks of improving the Russian economy while remaining communist and trying to spread communism across the globe. Stalin would make huge mistakes in his attempts to modernize Russia as the 5 year plan proved to be fundamentally flawed and the industry output was therefore weak. However, the sheer amount of what he was able to get Russia to produce (specifically in heavy industry), in spite of the inefficient system, would lead Russia to defeating Germany - a huge military and industrial force. Therefore, Stalin was successful to a certain degree in modernizing Russia.
A Soviet factory floor.