Adolf Hitler, among the most infamous and reviled leaders in world history, was named TIME Person of the Year in 1938.
"Hitler became in 1938 the greatest threatening force that the democratic, freedom-loving world faces today," the magazine said in early 1939 as it explained the choice.
The Nazi leader's aggression in Europe in the late 1930s shocked the region and the wider world, which was still weary from World War I.
In 1938, European leaders sought to appease Hitler as he pushed the region toward another major conflict by allowing him to annex the Sudentland, a region in what was then Czechoslovakia. Hitler had already annexed Austria earlier in the year.
The efforts to quell Hitler's imperialistic ambitions ultimately failed, and helaunched World War II with Germany's invasion of Poland in September 1939.
Joseph Stalin was chosen as TIME's Person of the Year in 1939 and 1942.
The Soviet leader is often pointed to as one of the most ruthless authoritarians in history.
Stalin was an influential figure of the era between his brutal, bloody rise to power in Russia as well as his central role in defeating the Nazis during World War II.
"The year 1942 was a year of blood and strength," TIME said of Stalin in early 1943. "The man whose name means steel in Russian, whose few words of English include the American expression 'tough guy' was the man of 1942. Only Joseph Stalin fully knew how close Russia stood to defeat in 1942, and only Joseph Stalin fully knew how he brought Russia through."
The latter half of 1942 and the early part of 1943 was a major turning point in the war due to the Soviet victory in the Battle of Stalingrad. Many historians consider it to be the greatest battle of World War II, as it stopped the German advance on the Eastern front and changed the entire outlook of the war for the Allies.
Nikita Krushchev became the leader of the Soviet Union with Stalin's death in 1953, and was named TIME Person of the Year in 1957.
He led the Soviets during a crucial part of the Cold War, including amid the Cuban Missile Crisis in 1962.
The US and the Soviets had been allies during World War II, but they quickly became adversaries as the globe's most powerful countries in the wake of the conflict.
In 1957, the US went into a panic after the Soviets launched the Sputnik satellites, marking the beginning of the space age and space race between the US and USSR.
As TIME explained its choice of Khrushchev for Person of the Year in early 1958, it wrote, "The symbols of 1957 were two pale, clear streaks of light that slashed across the world's night skies... With the Sputniks, Russia took man into a new era of space, and with its advances in the art of missilery, posed the US with the most dramatic military threat it had ever faced."
Former US President Richard Nixon was named TIME's Person of the Year in 1970 and 1971.
Nixon is undoubtedly among the most controversial presidents in US history at the time, due to the Watergate scandal, which led to his resignation in 1974 as he faced the prospect of impeachment. The cover-up and chaotic aftermath overshadowed any good he may have done as president.
When TIME picked him as Person of the Year for 1971, it discussed Nixon's famous visit to communist China and effort to pull the US out of Vietnam. But in what was perhaps an unintentionally foreshadowing description, TIME also referred to Nixon as "disconcertingly unpredictable."
Ayatollah Khomeini was TIME's Person of the Year in 1979, one of the most tumultuous years of the 20th century.
Khomeini was the central figure in the 1979 Islamic Revolution in Iran, which saw a pro-Western government ousted and involved the Iran Hostage Crisis at the US embassy in Tehran.
The politically active Shi'ite cleric had lived in exile for many years before a public uprising led the Shah of Iran, a US-backed monarch, to flee in early 1979. Khomeini returned shortly thereafter and spearheaded the establishment of a theocratic government based on Islamic law. He referred to the US as the "Great Satan" and dramatically altered the relationship between the two countries to this day.
In November 1979, Khomeini condoned Iranian students who seized the US embassy in Iran and took the staff hostage. The 52 American hostages were ultimately held in captivity for 444 days.
Writing on the decision to name Khomeini Person of the Year in early 1980, TIME said, "The lean figure of Khomeini towered malignly over the globe. As the leader of Iran's revolution he gave the 20th-century world a frightening lesson in the shattering power of irrationality, of the ease with which terrorism can be adopted as government policy."
The magazine added, "Khomeini's importance far transcends the nightmare of the embassy seizure, transcends indeed the overthrow of the Shah of Iran. The revolution that he led to triumph threatens to upset the world balance of power more than any other political event since Hitler's conquest of Europe."