Nicholas I was instrumental in helping to create an independent Greek state, and resumed the Russian conquest of the Caucasus by seizing Iğdır Province and the remainder of modern-day Armenia and Azerbaijan from Qajar Persia during the Russo-Persian War of 1826–1828. He ended the Russo-Turkish War (1828–29) successfully as well. Later on, however, he led Russia into the Crimean War (1853–1856), with disastrous results. Historians emphasize that his micromanagement of the armies hindered his generals, as did his misguided strategy. William C. Fuller notes that historians have frequently concluded that "the reign of Nicholas I was a catastrophic failure in both domestic and foreign policy." On the eve of his death, the Russian Empire reached its geographical zenith, spanning over 20 million square kilometers ( million square miles), but had a desperate need for reform.