Sen. Marco Rubio (R-Fla.) is a member of the Senate Foreign Relations Committee and the Senate Select Committee on Intelligence.

President Obama’s call on Wednesday for the United States to lead an international military campaign in the Middle East has the potential to begin a departure from the isolationism that he and former secretary of state Hillary Rodham Clinton have advocated during their years in office. There is a risk, however, that the president’s focus on a counterterrorism campaign akin to those waged in Yemen and Somalia, and his reliance on regional partners to deal with the challenge posed by the Islamic State, could lead to the continuation of what has been the most disengaged presidential foreign policy in modern American history.

From his focus on prematurely ending wars in the interest of “nation-building here at home” to his abandonment of America’s traditional allies in an effort to placate America’s enemies, President Obama has made it clear that he is different from his post-World War II predecessors. The question now is whether, facing this new threat, the president will rise to the occasion and truly reassert American leadership.

Five and a half years of the Obama/Clinton worldview has given Americans a graphic and often horrific view of the chaos that is unleashed in the world when America walks away from its traditional role as the guarantor of global security. From Syria and Iraq to eastern Ukraine and the South China Sea, we are seeing what the world will look like if our leaders continue choosing detachment: more violence, rivals and partners alike taking advantage of our inaction, and a steady increase in threats to our citizens and to our prosperity.

The Obama administration did not advocate this global retreat on its own. Members of my own Republican Party have also at times embraced the Democrats’ narrative that too much American leadership is the problem, rather than the solution to global instability. Not long ago, some neo-isolationists even claimed that America has no significant national interest in the conflicts in Syria and Iraq, and that American support for the Syrian opposition fueled the growth of the Islamic State.

The truth is that, when the Syrian people rose up in 2011 in protest against Bashar al-Assad’s brutal rule, our vital national interest was to prevent a protracted civil war in which radical jihadists from all over the world could rush into a vacuum. If they could seize operational spaces, they could use them to plan and carry out attacks against our allies and ultimately America.

In the early stages of this conflict, responsible, bipartisan voices called for U.S. leadership, hoping precisely to prevent the outcome we have now seen play out. I urged Secretary Clinton and President Obama to intervene decisively to oust Assad, and to identify and arm the moderate Syrian opposition. Instead, we were told that Assad was a “reformer” and that we should not get involved. At a critical decision point early in the Syrian crisis, when our involvement could have swayed the outcome, the isolationist voices won. America effectively stood on the sidelines, letting the problem fester for more than three years as the moderates opposing the regime were pushed aside by better-funded and better-armed jihadists. Meanwhile, the administration’s incoherent policy further empowered Assad, strengthening his grip on power as chaos, violence and refugees spilled across Syria’s borders, threatening the entire region.

Some former Obama administration officials, notably Secretary Clinton, have tried to argue that they advocated internally for a different approach, that they saw the train wreck coming. But when they were in positions of responsibility, they failed to prevent the situation that now exists. “What are we going to arm them with and against what?” Secretary Clinton said of the Syrian opposition in 2012. She and other administration officials who found their voices only after they left office were complicit in implementing and publicly defending the president’s disastrous foreign policies — and we’ll be dealing with the consequences for decades to come.

When President Obama finally proposed intervening militarily in Syria last year, his primary objective was to censure Assad for using chemical weapons. He argued that America should remain disengaged from the core conflict. He presented no viable plan to remove the Assad regime from power, significantly assist the moderate rebels or substantially degrade the radical jihadists.

More than three years into the conflict, we have done very little to support the non-jihadist opposition. After admitting in a late-August news conference that he had no strategy, the president now assures us that he has a plan to destroy the Islamic State. With any time wasted, the challenge only grows.

While the president abdicated leadership, other regional actors irresponsibly armed groups within Syria without regard for their ideology or goals. These nations chose to do so not because of U.S. involvement, but because of the lack thereof. The result is that today, Syria has become a prime operational space for radical jihadists from around the world.

With its base in Syria, the Islamic State is now perhaps the most extreme, powerful and capable terrorist group ever, with the clear intention of establishing an Islamic caliphate to dominate the region and launch attacks against anyone who doesn’t share its warped ideology.

The group didn’t achieve all this because America was too involved; just the opposite. It rose most quickly in America’s absence and is intent on driving us out of the Middle East. It is counting on us to abandon our support of Jordan, Israel and other allies. It plans to terrorize us into retreat.

America and the Islamic State are on an unavoidable collision course — and there will be a price as we finally confront this challenge. We should not think this struggle will be quick or risk-free. But every American should know that the price of further disengagement now would be greater sacrifice later.

To confront the Islamic State terrorists, we need a sustained air campaign targeting their leadership, sources of income and supply routes, wherever they exist. We must increase our efforts to equip and capacitate non-jihadists in Syria to fight the terrorist group. And we must arm and support forces in Iraq confronting it, including responsible Iraqi partners and the Kurds. In addition, we must persuade nations in the region threatened by the Islamic State to participate in real efforts to defeat it.

But we are fooling ourselves if we think that this will be just another counterterrorism campaign like the strategy the United States has pursued in Yemen and Somalia. Those cases are not success stories but containment strategies. The conflict in Syria is impossible to contain. The long-term threat posed by the Islamic State is much greater than that posed by al-Shabab or al-Qaeda in the Arabian Peninsula. If we are serious, as the president said, about ultimately destroying the Islamic State, we cannot rule anything out.

Part of our response should also be reflected in our budgetary discussions here at home. It is no coincidence that those Republicans who would continue the president’s failed isolationist policies would also accelerate another grave mistake of the Obama era: the weakening of our defense capabilities through misguided priorities and round after round of defense cuts, even as crises multiply. In their minds, a retreat on the world stage has the benefit of a smaller, less capable military to go along with it.

Taken together, a continued weakening of America’s role in the world in word and deed, and a reduction in U.S. military capabilities, would mark a dramatic and almost irreversible change in American foreign and national security policy — a change that would make the current chaos in the world pale in comparison.

As he “bears witness” to their violations of international order, President Obama likes to levy the charge that America’s foes, from Vladi­mir Putin to the Islamic State, are on the “wrong side of history.” But presidents are not supposed to be witnesses to history; they are supposed to help shape it in America’s favor. Those of us entrusted with public service are called to lead not in the world as we wish it were, but rather in the world as it is. The world is more connected than it once was, and recent history has proved that without American leadership, global instability threatens not only our national security, but also our economy and our very way of life.

Leadership demands shaping public opinion, not chasing it; speaking the hard truths on complex issues; and rallying the American people to confront the difficult challenges of our time. And those who seek to lead our country should understand that the world needs more American engagement, not less. Decisive and targeted use of America’s military, diplomatic and economic power will not only defeat the Islamic State and deliver us from this crisis, it will also strengthen America and ensure our long-term security.

A key lesson from President Obama’s first 51 / 2 years in office is that isolationism and disengagement, no matter how they’re disguised, only put more American lives at risk.

outlook@washpost.com

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