"Armed minorities" (74)

This refers specifically to groups like the pro-communist forces fighting a civil war against the Greek government at the time of the speech. The communist party was far from a "minority" in Greece, so Truman's labeling them as one was totally a political move.

Clifford-Elsey Report

This was a report written by two of Truman's BFF advisors, Clark Clifford and George Elsey, at the president's request in 1946, outlining Soviet-American relations. It was officially titled American Relations with the Soviet Union, but nobody remembers that.

What us historians (should) remember is that a lot of the report was "copy and pasted" into the speech that would become the Truman Doctrine. Elsey also claimed that this was the report that "hardened" Truman's stance on foreign policy towards the Soviets.

Cold War

The Cold War was the cultural, political, and ideological battle between the U.S. and the U.S.S.R. that dominated the second half of the twentieth century. It was considered a "cold" war because the two powers never directly fought each other, but instead funded a series of "hot" proxy wars between communist and anti-communist forces in other countries.

So it was sort of like that early Katy Perry song—it was hot then it was cold, yes and then no.

Containment

Containment was a Cold War strategy, or foreign policy theory, that said the only way to stop the Soviet Union was to put a lid on it, or contain it. The Truman Doctrine was a policy of containment, because it aimed to halt the spread of communism and Soviet influence in other countries.

Doctrine

A "doctrine" is a belief or set of beliefs or practices held by a church, political party, or some other fancy-schmancy group. In the context of U.S. history, presidential doctrines are attitudes, statements, or policies towards foreign affairs outlined by a President. Other policy "doctrines" besides Truman's include the: Monroe Doctrine, Roosevelt Corollary to the Monroe Doctrine, Eisenhower Doctrine, Reagan Doctrine, and the Tarkin Doctrine.

Domino Theory

The domino theory was a major Cold War political theory that said if one country in a particular region fell to communism, then the surrounding countries would also fall one-by-one (like a line of dominoes).

According to Truman Greece would lead to Turkey would lead to the Middle East would lead to (eventually) the Entire World lost to communism…if the U.S. didn't step in and do something about it.

Iron Curtain

What you cover your windows with if you really don't want any light seeping in.

It was also a term made famous in a speech by Winston Churchill. The iron curtain was an imaginary line that divided Europe after World War II. East of the curtain were countries connected to or influenced by the Soviet Union, while West of the curtain were member-countries of NATO and other anti-communist alliances.

Marshall Plan

A.k.a. "The European Recovery Program (ERP)."

The Marshall Plan was a proposal from Secretary of State George Marshall that offered economic support to rebuild post-war Europe. The Plan emphasized rebuilding European industry and re-establishing trade with the U.S. as a way to, once again, stop the spread of Soviet influence. The Marshall Plan was proposed a few months after the Truman Doctrine (June 1947) and irritated the Soviets even more.

"Outside pressures" (74)

A not-so-subtle shout-out to the Soviet Union. Truman never referred to them specifically in the speech, but context clues make it pretty clear who he sees as the big bad wolf threatening these poor, defenseless countries.

Totalitarianism

Totalitarianism is a political system marked by a central, often dictatorial government with unlimited power. A totalitarian regime gets its power from the widespread use of terror and often consists of single-party rule, a relentless propaganda campaign, and the silencing of free speech. (Think Big Brother in 1984.)

In his speech, Truman specifically referred to the need to "[help] free peoples" resist "totalitarian regimes," a.k.a. communist governments like the U.S.S.R. (64).