In the mid 1920s, after Lenin’s death, the Russian revolutionary Leon Trotsky took up the difficult task of defending the politics of socialism from below against the bureaucratic distortions perpetrated by Stalin’s rising bureaucracy. From then on until his assassination at the hands of a Stalinist agent in 1940, Trotsky devoted his life to rebuilding an international Marxist movement committed to reestablishing, and the onslaught of Stalinism, an authentically internationalist socialist current. And though there were difficulties and problems from which we can learn today—and which in particular led to problems in the Trotskyist movement after his death—his efforts were indispensable in keeping alive the traditions to which we continue to adhere.