President Trump marked a national observance on Wednesday for the millions victims who died as a result of international communism.

"On the National Day for the Victims of Communism, we honor the memory of the more than 100 million people who have been killed and persecuted by communist totalitarian regimes," the president said in a White House statement. "We also reaffirm our steadfast support for those who strive for peace, prosperity, and freedom around the world."

Communism, or Marxism-Leninism, is a political ideology whose adherents first seized power during the 1917 Bolshevik Revolution in Russia. Often referred to by the euphemism "scientific socialism," communism sought to reshape societies through collectivist systems that seek to change human nature through labor.

A main feature of communism is an implacable hostility to capitalism, the economic system that has produced the most advanced and freest civilization in human history.

Since then, "we have witnessed the effects of the tyrannical communist ideology—anguish, repression, and death," Trump said of the Bolshevik takeover.

"Communism subordinates inherent human rights to the purported well-being of all, resulting in the extermination of religious freedom, private property, free speech, and, far too often, life," he said.

States that adopt communist political systems are marked by violations of basic human rights. Resulting policies under communism have produced severe repression against any group or person perceived by ruling regimes to be an "enemy of the state."

China’s system has been noted as the deadliest communist state, producing a death toll estimated to be 65 million people through executions, forced labor, and other means, according to the authoritative Black Book of Communism, published in 1999.

China sought to reform its hardline communist system under Mao Zedong beginning in the 1980s by adopting quasi-capitalist features to its economy. Its political system, however, remains a repressive Leninist dictatorship.

According to the Black Book, more than 94 million people were killed or died as the result of communist regimes around the world, ranging from Russia to China to Cuba.

The victims included those who died in mass repression under communist systems through executions, government-produced famines, war, deportation, and forced labor.

Among the communist-inspired mass deaths have been the Soviet government-caused famine in Ukraine known as "Holodomor" that killed as many as 12 million people.

The Soviet purge known as the Great Terror from took place 1936 to 1938 when Stalin killed an estimated 700,000 land-owning peasants known as "kulaks" along with many political opponents.

Cambodia under the communist Khmer Rouge killed an estimated 2 million Cambodians.

Mr. Trump noted that many Germans in Berlin were shot crossing the Iron Curtain into Western Europe "as they tried to escape to freedom."

"The victims of these and many other atrocities bear silent testimony to the undeniable fact that communism, and the pursuit of it, will forever be destructive to the human spirit and to the prosperity of mankind," the president said.

"Today, we remember all who have been denied the great blessings of life, liberty, and the pursuit of happiness under oppressive communist regimes," Trump said.

"Together, we mourn the unbearable losses so many have endured under communism, and we renew our pledge to continue advancing the cause of freedom and opportunity for all."

The presidential message comes as many appear unaware of the legacy of communism.

A Gallup poll made public in August found that for the first time in over a decade of polling, Democrats favored socialism over capitalism.

Millennials also have shown greater interest in socialism, according to recent polling data.

A report by the Victims of Communism Memorial Foundation released last month concluded Americans need better education about communism and socialism.

"The American public lacks a serious understanding and education regarding socialism and communism," the foundation said in releasing the report.

"Most people continue to woefully underestimate the death toll of communism. It follows that only half of Americans can identify Cuba as a communist country, not to mention that 41 percent of Americans do not consider North Korea communist."

"As Marx and other leading socialists have made clear, socialism denies the concept of individual rights, rejects transcendent truth, and favors a collective understanding of justice," said Marion Smith, the foundation’s executive director.

"This system also now has a past record of practice in places like the USSR, China, Cuba, North Korea, and now Venezuela, among dozens of others around the world since 1917. Marxist governments have caused enormous political, economic, and humanitarian catastrophes—some of which continue today."

Democratic socialists, those who seek to impose socialism through elections, also have gained popularity in recent years.

Sen. Bernie Sanders (I., Vt.), a democratic socialist, gained popularity during his 2016 run for president, and Alexandria Ocasio-Cortez, a 29-year-old Democratic socialist was elected to Congress on Tuesday.

President Ronald Reagan, a strong anti-communist, along with Pope John Paul II who supported the anti-communist revolution in Poland in the 1980s were instrumental in exposing the reality of communism.

Soviet leader Mikhail Gorbachev also was a key reformer who helped bring down the Soviet Union that collapsed in December 1991.

However, anti-democratic Russian revanchists, including many Soviet-era security officials, rejected democratic reforms and led to a new non-communist dictatorship in Moscow under Russian President Vladimir Putin.

One of the most important voices in exposing the reality of communism was the late Russian writer and dissident Alexander Solzhenitsyn, whose 1974 book The Gulag Archipelago revealed the horrors of the Soviet system of forced prison labor, a main tool used to rid the Soviet Union of its opponents.