The Russian Revolution of 1917 was quickly perceived by both contemporaries and subsequent scholars as not merely a domestic event within the Russian Empire, but as a systemic crisis that fundamentally challenged the assumptions underpinning the existing international system. The revolution posed striking challenges not merely to conventional diplomacy, with the Bolsheviks openly seeking to end the war, spark international revolutionary class war, and vocally backing national self-determination for formerly subject peoples, but to existing social, economic, and ethnic orders. From nomadic peoples in Mongolia and the Central Asian steppe suddenly juggling new dilemmas of greater autonomy or full independence, to German workers, soldiers, and sailors challenging their traditional rulers, or Turkish politicians seeking to build a viable new nation state from the rubble of the Ottoman Empire, there were few political developments anywhere in the world in 1917–24 not directly or indirectly influenced by the Russian Revolution. The Arc of Revolution, which is Book 1 in the RGWR volume The Global Impacts of Russia’s Great War and Revolution, examines the reverberations of the Russian Revolution in the geographically contiguous imperial borderlands traditionally contested between Imperial Russia and its geopolitical rivals—the terrain stretching from Finland, through Central Europe to the Transcaucasus and Central Asia. Books 2 and 3 in the volume examine the wider global impact of the revolution in regions of the world noncontiguous with Russia itself, from North and South America to Asia, Africa, Australia, and various parts of Europe. The emphasis in Books 2 and 3, The Wider Arc of Revolution, is on the complex emotional appeal and ideological legacies of Russian communism, including anticommunism, evidenced well into the 20th century.