As a veteran, and as a governor who has supported Texas National Guard deployments to Iraq and Afghanistan, I can understand the emotions behind isolationism. Many people are tired of war, and the urge to pull back is a natural, human reaction. Unfortunately, we live in a world where isolationist policies would only endanger our national security even further.

That’s why it’s disheartening to hear fellow Republicans, such as Sen. Rand Paul (of Kentucky, suggest that our nation should ignore what’s happening in Iraq. The main problem with this argument is that it means ignoring the profound threat that the group now calling itself the Islamic State poses to the United States and the world.

In the Islamic State, which came to prominence in Syria and now controls ample territory, weapons and cash in both that country and Iraq, the world is confronting an even more radicalized version of Islamic extremism than Al-Qaida. This group is well-trained, technologically sophisticated and adept at recruitment, with thousands of people with European passports fighting on its side, as well as some Americans.

This represents a real threat to our national security — to which Paul seems curiously blind — because any of these passport carriers can simply buy a plane ticket and show up in the United States without even a visa. It’s particularly chilling when you consider that one American has already carried out a suicide bombing and a terrorist-trained European allegedly killed four at the Jewish Museum in Brussels.

Yet Paul still advocates inaction, going so far as to claim in commentary last month in the Wall Street Journal that President Ronald Reagan’s own doctrines would lead him to same conclusion.

But his analysis is wrong. Paul conveniently omitted Reagan’s long internationalist record of leading the world with moral and strategic clarity.

Unlike the noninterventionists of today, Reagan believed that our security and economic prosperity require persistent engagement and leadership abroad. He, like Eisenhower before him, refused to heed “the false prophets of living alone.”

Reagan identified Soviet communism as an existential threat to our national security and Western values, and he confronted this threat in every theater. Today, we count his many actions as critical to the ultimate defeat of the Soviet Union and the freeing of hundreds of millions from tyranny.

At the time, though, there were those who said that Reagan’s policies would push the Soviets to war. These voices instead promoted accommodation and timidity in the face of Soviet advancement as the surest path to peace. This, sadly, is the same policy of inaction that Paul advocates today.

In the face of the advancement of the Islamic State, Paul and others suggest the best approach to this 21st-century threat is to do next to nothing. I personally don’t believe in a wait-and-see foreign policy for the United States. Neither would Reagan.

Reagan led proudly from the front, not from behind, and when he drew a “red line,” the world knew exactly what that meant.

Paul is drawing his own red line along the water’s edge, creating a giant moat where superpowers can retire from the world.

We have seen President Obama draw his red lines, but the world knows by now that this is a rhetorical device or negotiating ploy rather than a promise of action. This kind of confused leadership and passivity enabled groups such as the Islamic State to grow and play major roles in terror’s resurgence. It has also enabled Al-Qaida to regroup.

As a consequence, there are no good options in Iraq or Syria. The window to shape events for the better passed years ago. The lousy choices we face today are the price of failed leadership. Nonetheless, the president can and must do more with our military and intelligence communities to help cripple the Islamic State. Meaningful assistance can include intelligence, surveillance and reconnaissance sharing and airstrikes.

In the aftermath of the attacks of Sept. 11, 2001, many national-security leaders lamented the fact that more hadn’t been done to track down Osama bin Laden. In the Islamic State, we face what could be an even more sophisticated enemy. Who can doubt that other bin Ladens are lurking in the labs and training grounds of this group’s newly gained territory?

Viewed together, Obama’s policies have certainly led us to this dangerous point in Iraq and Syria, but Paul’s brand of isolationism (or whatever term he prefers) would compound the threat of terrorism even further.

Ignoring the growth of the Islamic State and events in Syria and Iraq will only ensure that the problem will fester and grow. The United States needs to take seriously the threat this presents to our nation.

Paul is an articulate advocate for his views, which are shared by many on the left and some on the right. But in today’s world, with today’s threats, we still cannot “take blind shelter across the sea, rushing to respond only after freedom is lost.” That was President Reagan’s warning. Sen. Paul would be wise to heed it.

Rick Perry, a Republican, is governor of Texas. He wrote this article for the Washington Post.