The fourth year of fighting brought several of the combatants to the point of collapse. France, Italy, and Russia discovered that their military forces were no longer stable organizations. Events on the home front now took on crucial significance, most notably in Russia, where the governing system itself fell victim to the strains of the fighting. At the same time, older features of the war continued. The war spread to bring in new belligerents, the crucial newcomer being the United States. Moreover, the massive and seemingly futile bloodletting on the western front did not abate; the carnage took its most hideous form at the Third Battle of Ypres (Passchendaele).