Douglas Brinkley is CNN's Presidential Historian. This article is adapted from his book, "The Unfinished Presidency: Jimmy Carter's Journey to the Nobel Peace Prize." The opinions expressed in this commentary are his.

(CNN) Word that Jimmy Carter has cancer reminded me of something that his White House Chief of Staff Hamilton Jordan once said about his boss: He was "indefatigable," able to rebound from adversity as if a gutsy superhero.

"I have always believed that it is a sign of weakness to show emotion, giving in publicly to despair, frustration, or disappointment," Carter wrote in his 1982 memoir "Keeping Faith."

"I try to hide my own feelings to reassure others by emphasizing the positive aspects of the situation and to pray for strength and wisdom. Privately I commit myself to overcoming obstacles or to figuring out a new course of action."

Carter's never-throw-in-the-towel personality was fomented during his U.S. Navy years (1943 to 1951). The only 20th-century president who had a longer military career than Carter was Dwight Eisenhower. Because Carter refused to bomb Tehran during the Hostage Crisis of 1979--81, his critics painted him as a Cold War weakling. But this is the wrong way to look at his presidency.

Using human rights as this sword, Carter, as president, bolstered America's credibility by lambasting the Soviet bloc countries and other totalitarian nations for crimes against freedom. "I believe historians and political observers alike have failed to appreciate the importance of Jimmy Carter's contribution to the collapse of the Soviet Union and the end of the Cold War," former Secretary of Defense and CIA Director Robert Gates maintains in his memoir "From the Shadows."

"He was the first president during the Cold War to challenge publicly and consistently the legitimacy of Soviet rule at home. Carter's human rights policy ... by the testimony of countless Soviet and East European dissidents and future democratic leaders, challenged the moral authority of the Soviet government and gave American sanction and support to those resisting the government."

Unfortunately a mythology has taken root that Carter, as president from 1977--1981, was weak on defense. As National Security Adviser Zbigniew Brzezinski has rightly maintained, Carter strengthened and modernized the U.S. military during a very difficult post-Vietnam War period, when the Pentagon was deeply unpopular. Just months after Carter entered the White House, he began badgering our NATO allies to rearm. In fact, he demanded solid commitment from every member to increase their defense budgets by 3% a year.

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When the Soviets started manufacturing SS-20 nuclear missiles, it was Carter who countered by proposing that NATO cruise and Pershing missiles be based in Western Europe. And far from slashing American armed forces in Europe, Carter deployed an additional 35,000 troops to boost the American NATO contingent above 300,000, which more than made up for the cuts the Nixon and Ford administrations had made under détente. Besides modernizing NATO, Carter approved deployment of both nuclear cruise missiles and the Pershing II IRBMs -- intermediate-range nuclear forces -- in Europe.

Carter had no intention of appeasing the Soviets. In fact, his very concentration on human rights was in part intended to weaken the Kremlin. Where Gerald Ford had refused to welcome exiled Russian author Aleksandr Solzhenitsyn to the White House, Carter embraced political dissidents Vladimir Bukovsky and Andrei Sakharov with open arms.

Perhaps the most profound document on display at the Carter Presidential Library in Atlanta is the February 5, 1977 missive he sent to Sakharov: "Human rights is the central concern of my administration," Carter wrote. "You may rest assured that the American people and our government will continue our firm commitment to promote respect for human rights not only in our country, but also abroad."

This epistle, which the Nobel Prize-winning physicist proudly waved in President Leonid Brezhnev's face, prompted the Soviet leader to pronounce Sakharov an enemy of the state. As Robert Gates noted, "Whether isolated and little-known Soviet dissident or world-famous Soviet scientist, Carter's policy encouraged them to press on."

Furthermore, it was Carter -- not Reagan -- who first capitalized on the human rights provisions of the Helsinki Accords in order to allow movements such as Czechoslovakia's Charter 77, Poland's Solidarity, and the Helsinki Watch groups in East Germany and the Soviet Union to flourish. Czech Republic President Vaclav Havel even avowed that Carter's vigorous human rights stance so undermined the legitimacy and self-confidence of the Warsaw Pact chieftains that dissidents across Eastern Europe regained the hope that carried them on to post-1989 democracy.

Lech Walesa professed that it was Carter's tough December 3, 1980, statement -- which warned the Soviets about the consequences of their military buildup on the Polish border -- that sent a signal that, unlike Czechoslovakia in 1968, the United States would not abandon "anti-Socialist" forces in Poland. And that wasn't all: Carter's human rights policy also created an environment that allowed 118,591 Soviet Jews to emigrate during his presidency, and encouraged Indonesia to release some 30,000 political prisoners from jail.

Under Carter's direct order, the CIA began covertly smuggling into the Soviet Union and Eastern Europe literature about democracy and books like Aleksandr Solzhenitsyn's "The Gulag Archipelago." Perhaps even more inspired, Carter had the CIA infiltrate the Soviet Union with thousands of books promoting the heritage of ethnic minorities. All in all, the Carter administration's insistence on human rights saved thousands of lives and put the Soviets in a defensive crouch. And, before long, Soviet-style communism collapsed, thanks, in part, to Carter's brave promotion of human rights.

As the world prays for Carter to become a cancer survivor, we should remember the raw courage behind his standing up to the Soviets.

Even at 90 years old, Carter remains a freedom fighter and a respected leader and a warrior for peace. Two lines from his favorite poet, Dylan Thomas, perfectly capture his unyielding rectitude in recent years in trying to stamp out preventable diseases (like river blindness and Guinea worm in Africa) and in promoting global democracy in the 21st century via the Carter Center: "Do not go gentle into that good night / Old age should burn and rave at the close of day."

Rave on, Jimmy Carter, against cancer -- perhaps the worst scourge of all. The freedom-loving world is on your side.