Today marks the 30th anniversary of the inauguration of U.S. President Ronald Reagan. One wonders how the man who, by sheer force of belief, ended the Cold War without a shot being fired would have responded to 9/11 and to the global financial crisis.

Born in a rented apartment in Tampico, Illinois, few could have predicted that the son of a shoe salesman would become one of the most revered political figures of his generation. His first career was as an actor with Warner Bros., spending many years featuring in B-movies, where, he joked, “the producers didn’t want them good, they wanted them Thursday.”

When the 69-year-old Reagan became president, he encountered a barrage of intellectual snobbery from the European and East Coast establishments. The then British ambassador to the U.S., Sir Nicholas Henderson, opined that “Reagan believes there are simple answers to complex problems. The main worry is not just age, but whether he possesses the mental vitality and political vision necessary.”

But Reagan proved them all wrong. He became the first Cold War president to serve two terms without becoming involved in a major armed conflict, despite it being an extraordinarily unstable and volatile period in world history.

Just over a year before Reagan took office, Soviet forces had invaded Afghanistan. Beyond Afghanistan, the escalation of proxy regional conflicts in Nicaragua, Angola and Ethiopia further strained the U.S.-Soviet relationship. Relations deteriorated further in 1983 when Moscow terminated arms-control negotiations, raising the prospect of a nuclear-arms race.

Many in the West supported a return to détente with the Soviet Union. However, Reagan abandoned this policy and, together with British Prime Minister Margaret Thatcher, he spoke up for freedom, criticizing the oppression within the Soviet Union. He described the U.S.S.R. as an “evil empire” and predicted that “freedom and democracy will leave Marxism and Leninism on the ash heap of history.”

When Soviet fighters shot down a Korean Airlines plane in 1983, killing 269 people, Reagan called it a “massacre” and publicly condemned the Soviets for turning “against the world and the moral precepts which guide human relations among people everywhere.” In President Reagan and Prime Minister Thatcher, the West had two leaders who believed in clarity of principle, simplicity of language, and who were unflinching in their beliefs.

Reagan’s tough rhetoric appalled critics, who accused him of warmongering and urged a return to peaceful co-existence with the US.S.R. Reagan, though, believed in the inevitable triumph of democratic values over dictatorships. He would not settle for mere détente. Nor did Reagan confine his attacks on the Soviet system to his speeches. He backed up his rhetoric with hard-headed action, such as providing financial support to anti-Communist groups across the world.

The Soviet Union was the most serious threat to the U.S. during Reagan’s presidency, but it was not the only threat. Terrorist attacks on U.S. targets were a common occurrence. In 1986, a bomb planted by Libyan agents exploded in a West German discothèque, killing two American servicemen and wounding 200 civilians. Reagan took decisive action, launching air strikes against Libya, again to the horror of many European governments.

Far from entrenching longstanding Cold War hostilities, it was Reagan’s courageous decision to tackle communist ideology head-on that made the transformation of U.S.-Soviet relations possible.

Historians point to the close personal relationship between Reagan and former Soviet leader Mikhail Gorbachev as a major factor in the peaceful conclusion of the Cold War. But this relationship was not always an easy one. Reagan used all his diplomatic skills to create mutual trust. In 2004, reflecting on his cordial relationship with Reagan, Mr. Gorbachev commented: “Look at how it began. When I was first asked what I thought of Reagan, I called him a dinosaur. He called me a Bonehead Bolshevik.”

Reagan was prepared to take a firm stand in the domestic arena too. In the first year of his presidency, U.S. air traffic controllers broke federal law by going on strike. Reagan responded by giving the strikers 48 hours to return to work or face the consequences, sacking the 11,000 who refused to comply.

He also tackled the U.S. economic malaise, reversing years of rising inflation and unemployment. While many favoured a financial stimulus to increase the money supply, Reagan cut taxes, reduced regulation, and abandoned Nixon’s wage and price controls. The result was a sustained period of economic expansion during which the U.S. economy grew by more than a third. Every income group became wealthier, and consumer confidence soared.

So how would Reagan have responded to the major threats of the 21st century? No doubt, in response to Islamic terrorism, he would have flown the flag of freedom. He would have asserted the importance of Western, democratic values, rather than undermining them through the use of torture, control orders and the erosion of traditional freedoms in the name of national security.

In response to the financial crisis, Reagan would have emphasized that the roots of economic recovery lie not in financial stimulus packages, but in a return to the principles of free enterprise, lower taxation and deregulation. Above all, Reagan would have used his communication skills to convince people that these values and principles are strengths, not weaknesses to be given away.

In contrast to Sir Nicholas Henderson’s view that Reagan was too simple to be up to the job, it was precisely Reagan’s simplicity of language and clarity of views that made his insights and policies so powerful.

Mr. Davis is a member of Parliament.