As the Syrian civil war moves inexorably toward a sixth year of conflict, calls for US intervention are once again on the upswing. Advocates of increased intervention in the conflict focus on Syria’s humanitarian tragedies, or on the need to oppose Russia. Underlying most of their arguments is the simple assumption that American intervention could improve the lives of Syria’s citizens and bring a swift end to the conflict, if we only had the political and moral will to do so.

Yet that assumption is fundamentally mistaken. Further US intervention has little chance of succeeding, and in fact is far more likely to worsen the conflict.

The desire to lower the horrifying humanitarian costs of Syria’s bloody civil war is laudable. More than a quarter million Syrians have died in the past five years, and more than 6.6 million have been internally displaced. The United Nations estimates that at least 18 towns or cities are effectively besieged, preventing their civilians from receiving supplies of life’s basic necessities.

The situation has only been worsened by Russia’s recent entry into the conflict. As United Nations Secretary General Ban Ki-moon recently noted, only 620,000 Syrians were able to receive aid from UN-coordinated aid convoys last year, compared with 2.9 million in 2013.

Other reasons cited in favor of intervention are similarly comprehensible. While it would be foolish in the extreme to intervene in Syria’s civil war simply to oppose Russia, it is true that facts on the ground can shape diplomatic outcomes. Progress against either Assad or extremist groups by a strong US-supported rebel group on the ground could improve our leverage in the Geneva process. Meanwhile, the potential for Syria’s turmoil and resultant refugee crisis to be regionally destabilizing remains a strategic concern for American policymakers.

Yet whatever the motives, the core of each pro-intervention argument is the idea that further American involvement — whether in the form of support for rebel groups, the creation of a no-fly zone, or even the use of American forces inside Syria — has the potential to substantially improve the situation inside Syria.

It’s an easy assumption to make; after all, America’s military is the strongest in the world, and our involvement has reshaped various conflicts over the past 50 years, in ways both good and bad. Yet in the context of Syria’s intractable political rivalries and geopolitical realities, it is a mistaken assumption. US intervention is likely only to aggravate and lengthen Syria’s conflict.

Put bluntly, the US military can’t fix Syria.

Take, for instance, the frequently proposed idea of creating a no-fly or humanitarian safe zone where civilians could receive humanitarian aid and protection from indiscriminate bombardment. On the face of it, this sounds appealing. Unfortunately, there are simply too many practical obstacles to successful implementation.

A safe zone that covers the area 10 to 20 kilometers south of the Turkish border — a common suggestion — wouldn’t actually protect the civilians most at risk from bombardment, while expanding the zone south toward civilians in Aleppo would bring US forces into direct confrontation with Russian air forces and possibly even Syrian air defenses.

Then there’s the problem of differentiating civilians from rebel fighters. Without a sizable ground force, it will be impossible to prevent Syria’s many armed factions from using the zone as a training ground or safe haven.

Troops from Turkey, Saudi Arabia, or other regional allies, whose governments have backed rebel groups against the Assad regime for years, even have an incentive to allow rebel groups to use the zone in this way. The inevitable attacks conducted on Russian or Syrian government troops using the safe zone as a base would encourage Russia to retaliate, dramatically increasing the likelihood of direct conflict between US and Russian air forces.

Worst, even if all these obstacles were overcome — an extremely unlikely scenario where Russia offers no resistance and the US contributes a large-scale troop presence on the ground to enforce the zone — a no-fly or humanitarian zone wouldn’t actually solve Syria’s underlying problems. Instead, it would create Russian and American zones of interest, broadening the conflict and prolonging it perhaps indefinitely.

In fact, lengthening the conflict by creating a military stalemate is a major flaw in most proposals for further US intervention, including giving more arms to Syrian opposition groups. Again, there are many reasons to be wary of further arming the rebels, including the risk that the weapons will fall into extremist hands. But the biggest problem remains simply that more arms will not bring an end to the conflict. Even a strong, united opposition would struggle to effectively take on Assad and his Russian backers, and the opposition is anything but united.

It is hard to overstate the extent to which Syria has become a war of all against all, including fighting even between Syria’s main Kurdish and Sunni opposition groups. The weak and fragmented nature of the Syrian opposition has become increasingly visible as it becomes apparent that even groups receiving US backing are now beginning to fight each other. As various sarcastic headlines have noted, at this point we are effectively in a proxy war with ourselves. The opposition will not suddenly and miraculously work together if given more weapons; such aid will only increase the duration and brutality of the conflict.

No form of US intervention can fix Syria’s fundamental problems: fragmentation, internecine infighting, and the utter lack of any unified anti-Assad coalition. And though some observers have focused on Russia’s recent military gains to argue that US military force can succeed in Syria, their analogy is flawed. Russia has a defined ally —ground forces in the form of Syrian government troops and Iranian militias — and a clear goal, to reassert regime control.

The United States has none of these things. Russian success has also flowed from its indiscriminate bombing of civilian areas, a brutally effective technique that has allowed the regime to retake territory. Thankfully, the American military’s rules of engagement do not permit such barbaric actions.

Even the most extreme and unrealistic option — a massive ground invasion by US troops to topple the Assad regime and defeat ISIS — cannot create a coherent Syrian state acceptable to the people of Syria and to our squabbling allies. Such an invasion would require a decade-long occupation by US forces. Insurgency, instability, and the many other failures of state building in Iraq and Afghanistan would undoubtedly be repeated in Syria, magnified by the fissures of five years of brutal civil war.

The risks associated with further US intervention in Syria are significant, including the potential for a direct conflict with Russia, or for broader regional war. Yet in focusing on the large potential costs, debates on US-Syria policy too often overlook the fact that further intervention will provide few if any benefits. It is easy to critique the Obama administration’s inaction on Syria and the pursuit of diplomacy over intervention that has allowed Russia to occupy a dominant role in Syria’s future.

Given a choice between pursuing a flawed diplomatic settlement now on Russia’s terms, or the potential for a marginally better settlement following several more years of intervention and bloody conflict, the administration has consistently chosen to accept the lesser of two evils. This focus on diplomacy backed by humanitarian efforts may also have a low probability of ending the Syrian civil war, at least in the near term. But unlike most of the alternatives, the White House’s current strategy can help lay the groundwork for a future diplomatic settlement. And unlike the alternatives, it will do so without ratcheting up the conflict inside Syria.

In choosing this approach, the president and his advisers seem to have understood what many of their critics have not: Increased US intervention has the potential to prolong and worsen Syria’s civil war, but not necessarily to improve it.

Emma Ashford is a visiting fellow in defense and foreign policy studies at the Cato Institute. Find her on Twitter @EmmaMAshford.