It has often been mentioned that Germany felt pressured to attack when it did because it was fearful that Russia would have economically and militarily surpassed it in 10 years or so. Now I have heard some things of the Russian military reforms which were supposed to be very promising. But what happened in this reform? And on economic terms, what were the expectations of Russia's growth? Where did this seemingly sudden growth come from?
This is a matter of debate for Russian historians, especially so considering the years leading up to 1914 in Russia were (to say the least) an extremely contentious time.
Russia's economy had been growing quickly since the 1890s, and was accelerating after the 1905 revolution. While Russia remained backwards compared to the rest of Europe both industrially and agriculturally, mass media in the day portrayed Russia as a looming colossus, ready to engulf Europe. Why?
Well, Russia was embarking on a variety of reforms that some historians maintain would have charted a path towards true western style industrialization for Russia during the 1910s. This is supported by the increasing privatization of village lands in this years, and the increase in larger non-aristocratic holdings. Agriculture was beginning to improve, and the peasantry may have been entering a permanent decline. Industrially, Russia was driven by massive investment by elites but also by British and German business owners. While still dependent on foreign investment, Russia's industries, despite only employing a small percentage of the total population, still were large enough to put them on the same playing field as Germany and the UK. Similarly, the Russian military benefited from large arms purchases abroad, combined with a large domestic military industry. While still more primitive compared to the German or British army, the Russians could (and often did) hold their own in World War 1, barring the disastrous defeats early in the war.
This brings me to the most obvious point - the Russian Empire before 1914 was big. Like really big. It had the third largest population in the world, massive amounts of resources and land, and an extremely creative and intelligent class of scientists, artists, and writers. If Russia had avoided revolution, and industrialized into a stable constitutional state, there's no doubt that the projections of Russian power would have come true. In some sense they did anyway - some historians argue that the Soviets simply continued modernization projects started under the Tsar, except at a far hastened rate. However, the Russian state was of course drastically changed in its political and economic outlook by the Bolsheviks - who also were not averse to using force to achieve rapid modernization.
If you have a helluva lot of time on your hands, read Orlando Figes' A People's Tragedy: The Russian Revolution 1891-1924. It's like a billion pages long but it'll tell you everything you'd want to know about this period.