Chinese President Xi Jinping speaks during an event to commemorate the 40th anniversary of the Message to Compatriots in Taiwan at the Great Hall of the People in Beijing on Wednesday. (Mark Schiefelbein/AFP/Getty Images)

Former president Jimmy Carter’s Jan. 1 op-ed, “How can we avoid a modern-day Cold War,” was thoughtful and important. However, intentionally or not, there was no mention of the flood of the deadly drug fentanyl into the United States from China. Some might argue the fentanyl invasion is an act of war, and certainly it requires a much more aggressive response from the United States than has been demonstrated so far. 

As we begin a new year, it is important to understand that a stealth World War III has been well underway, with aggression toward the United States at its center. The threat from militant Islamists has not gone away. Behind the facade of civil, if not friendly, behavior, Russia has been doing its best to undermine U.S. democracy by, among other covert efforts, corrupting the electoral process. China, itself a previous victim of massive opioid addiction orchestrated by England in the 19th century, has been complicit in the poisoning of U.S. citizens. 

As 2019 begins, the United States is under siege — not in a Cold War, but a World War.

Harry Flickinger, Bethany Beach, Del.

Former president Jimmy Carter is proud of his role in establishing relations with the People’s Republic of China. But, worried about deteriorating relations between China and the United States, he reverted to the submissiveness and moral equivalence that characterized his presidency and put the free world at risk before a totalitarian competitor.

Mr. Carter described the United States and China in neutral terms, as two essentially similar economic superpowers that must find a modus vivendi, ignoring the fundamental differences between the two societies, including China’s devastating human rights abuses and increasingly aggressive militarism. As if to answer the former president, on Wednesday, President Xi Jinping, calling forth Marxist-Leninist historical determinism, said unification with Taiwan was “the great trend of history” and continued: “We make no promise to abandon the use of force, and retain the option of taking all necessary measures.”

Forty years ago, American leaders normalized relations with Communist China in the hope that China would prove a good citizen of the international community, but, sadly, that has proved not to be the case. In this situation, more moral clarity and strategic resolve than Mr. Carter can muster are needed, for the sake of both the Chinese and American people.

Jianli Yang, Washington

The writer, a survivor of the 1989 Tiananmen Square Massacre and political prisoner of China from 2002 to 2007, is founder and president of Citizen Power Initiatives for China.