Leader of the Soviet Union

During the history of the Soviet Union, there was no office entitled "Leader" of the Soviet Union. The General Secretary of the Communist Party of the Soviet Union was "leadership" position of Soviet Union for most of the country's history.

Vladimir Lenin wanted the executive be a collegiate body dominated by the Communist Party. Throughout the 1920s, however, Joseph Stalin shaped the minor bureaucratic position of General Secretary into the party's de jure leader, and in turn made the office into the Soviet Union's de facto leader. Even though Stalin was not formally re-elected to the position by the 17th Party Congress in 1934, he remained the Soviet Union's undisputed leader, becoming the country's head of government in 1941. He never became the de jure head of state.

After Stalin's death in 1953, the country was ruled by a troika until Nikita Khrushchev assumed sole power under the title "First Secretary". Like Stalin, Khrushchev served a term as the country's head of government from 1958 to 1964, though, like Stalin, his true power stemmed from his First Secretary position.

When Khrushchev was deposed in 1966, the office of General Secretary was re-created by Leonid Brezhnev, whose powers were checked by the party's collective leadership for a time. But by 1977, Brezhnev had succeeded in expanding the powers of the General Secretary, and became the Soviet head of state (a position he'd previously held during Khrushchev's reign). The combination of General Secretary and head of state was continued by Yuri Andropov (1983-1984) and Konstantin Chernenko (1984-1985). Mikhail Gorbachev became the General Secretary in 1985, but he did not become head of state until 1988. After Gorbachev survived a coup attempt in 1991, he saw no choice but to step away from the General Secretary position. He remained President of the Soviet Union until the country collapsed in December, 1991.

Because the title "General Secretary of the Central Committee of the Communist Party of the Soviet Union" is so awkward, and because the structure of power in the Soviet Union can be confusing at times, the category's name has been simplified.

Joe Steele
Vladimir Lenin oversaw the establishment of the Soviet Union with the former Russian Empire at its nucleus. After his death, he was succeeded by Leon Trotsky, who imposed an authoritarian regime in the pursuit fulling a global Marxist revolution. Trotsky oversaw his country's triumph over Nazi Germany during World War II, and expanded the USSR's reach into Eastern Europe and Southeast Asia.

He and U.S. President Joe Steele shared a deep hatred for each other until Steele's death in 1953.

Worldwar
Joseph Stalin had ruled the Soviet Union for nearly 20 years when first World War II broke out. Before the war could be ended, the global situation became more dire with the arrival of the Race, whose Conquest Fleet invaded Earth, forcing former enemies to become allies of necessity. Stalin's mixture of stubbornness and ruthlessness helped insure his own country's survival when the fighting stopped in 1944.

Stalin died nine years later. He was succeeded as General Secretary by Vycheslav Molotov, who had served as Foreign Commissar since 1939. Molotov was a more cautious leader than Stalin, avoiding conflict and military "adventurism". However, he did not engender the same level of fear in his subordinates that Stalin had. He faced a coup attempt from NKVD head Lavrenty Beria in 1963. Molotov was imprisoned for about 24 hours before the Soviet Red Army toppled Beria. Molotov was dependent upon Marshal Georgy Zhukov. When Molotov died in 1986, he was the last politician of the original Race invasion extant.

Other Leaders
In addition to the works above, Joseph Stalin is or was the ruler of the Soviet Union in a substantial number of Turtledove works, especially those set during World War II or with points of divergence involving Word War II, including The Hot War, In the Presence of Mine Enemies, The Man With the Iron Heart, "The Phantom Tolbukhin", "Ready for the Fatherland", and The War That Came Early.

In the Presence of Mine Enemies is set in a world where the Axis won World War II. Stalin appears to have been killed in the 1940s, and seems to have been the last leader of the Soviet Union. In "Ready for the Fatherland", Stalin's death in March, 1953 is referenced, but his successors are unnamed. The Hot War is an alternate history trilogy depicting a Third World War breaking out as a result of the Korean War. The series is ongoing, with the first two volumes covering the period between November, 1950 to May, 1952.

In A World of Difference, which is set in 1990 in a timeline where the planet Mars was replaced by the planet Minerva, Leonid Brezhnev is posthumously referenced, as is Mikhail Gorbachev, who died prematurely, almost certainly at the hands of the KGB.

In The Gladiator, which is set in the 2090s of a timeline where the Soviet Union won the Cold War, Vladimir Putin is explicitly mentioned as having been General Secretary and being a hero of communism along with Lenin and Stalin. As the earliest POD identified is the Cuban Missile Crisis, Nikita Khrushchev also probably ruled, but he isn't specifically named.

Historical Leaders in Non-Leadership Roles
Several historical Presidents have appeared in the works Harry Turtledove in a capacity other than as de facto leader of the USSR.

Joseph Stalin is referenced by his nom de guerre, the "Man of Steel" in the The Center Cannot Hold. He's a Red general in the Southern Victory timeline's version of the Russian Civil War. While we don't know his final fate, the Tsarists win the war, and Stalin does not come to power. In the Joe Steele timeline, Stalin is born in the U.S. and becomes President Joe Steele.

Nikita Khrushchev directly appears in the Worldwar franchise series Colonization and is referenced in Homeward Bound. In Colonization, he is the General Secretary of the Communist Party of the Ukrainian Soviet Socialist Republic, a position subordinate to the actual Soviet leader, Vyacheslav Molotov. While we learn he promises to bury the Race in Homeward Bound, much as he did the United States in OTL, he never appears to have actually become the leader of the USSR. Khrushchev also directly appears in the short work "The Phantom Tolbukhin", serving as a political officer with Fedor Tolbukhin's guerrilla band as they battle German occupiers in 1947. Khrushchev is mentioned briefly in The War That Came Early: Hitler's War, but that series ends in 1944 with Stalin still in power.

Mikhail Gorbachev appears in the guise of "Mikhail Sergeyevich" in Colonization: Aftershocks as a protocol officer at the Soviet embassy in Little Rock. There is no reason to think he came to power in that timeline. He holds a similar position under the same name at the Russian embassy in Victoria, North American Union in The Two Georges.