How did Russia lose its dynasty and nearly its country?

When the last tsar of the Rurik dynasty died without an heir in 1598, nobody had an accepted right to the throne, and the country slid into fifteen years of civil war, famine and foreign occupation. Feodor I, a weak and possibly intellectually disabled ruler, took little interest in politics and ruled through his adviser Boris Godunov. His death ended the main line of the Rurik dynasty, which, in a historian's words, was the only ruling dynasty Moscow had ever known. Godunov was crowned in September 1598 and, according to the historian Chester Dunning, had himself 'elected' after the fact by a sham assembly.

Then nature struck. Between 1601 and 1603 a famine, potentially caused by the eruption of the Peruvian volcano Huaynaputina, brought extremely poor harvests, with summer nights often below freezing. Famine and the disease that followed are said to have claimed a third to two thirds of the population, a very wide estimate.

Into this gap stepped the impostors. Rumors said Feodor's younger brother Dmitry was alive, despite official accounts that he had been stabbed to death as a child. In 1603 a man claiming to be Dmitry appeared in the Polish–Lithuanian Commonwealth. After Godunov died in 1605, this False Dmitry I entered Moscow in triumph and was crowned, only to be killed by armed mobs on 17 May 1606, ten days after his wedding. More False Dmitrys followed.

By around 1610 Russia was a failed state, with the throne vacant and Catholic Poles in the Kremlin. A butcher from Nizhny Novgorod, Kuzma Minin, collected taxes to fund a second militia led by Prince Dmitry Pozharsky. And on 21 February 1613 an assembly elected 16-year-old Mikhail Romanov as tsar, founding the Romanov dynasty. Estimates of the deaths caused by the fighting itself run from 1 to 1.2 million.