This piece was co-authored by Michael Rubin, resident scholar at the American Enterprise Institute. Read the full article on Lawfare.

While the worst violence of Syria’s six-year-long war may be over, a credible settlement is still far off. The Trump administration has boosted the U.S. military presence in Syria. While this enhances Washington’s leverage, it will not alone assure long-term U.S. interests: The destruction of the Islamic State, a cessation of Syria’s destabilizing refugee flow, and an end to Syria’s transformation into a logistical hub for expanding Iranian and perhaps Russian influence.

To achieve these aims, Washington needs a more holistic approach toward external powers now involved in the Syrian conflict. During the campaign, Trump suggested working with Russia to fight the Islamic State; his secretary of defense seems disinclined to follow through on that proposal. But much of U.S. policy will hinge on the influence of other regional players, Iran and Turkey. Both have vested interests in Syria that do not align well with those of the United States, and the Trump administration will have to manage these unreliable actors carefully as the conflict continues.

Regional Rivalries Persist

Both Iran and Turkey vested in the outcome of the war and justify their military interventions on grounds of national security. The Iranians, relentless backers of Bashar al-Assad’s regime, tout that the 30,000-man armed force they say they directly control are engaged in an “existential” struggle against the Islamic State. In reality, Tehran has overwhelmingly fought non-Islamic State opposition forces along the border with Lebanon, in effect consolidating a land bridge for Hezbollah, Tehran’s most cherished Arab proxy. 

Iran’s multi-billion dollar campaign to save Assad is far more about maintaining Syria as a forward base for Tehran’s broader regional ambitions than defeating the Islamic State. Recent amassing of Iran-backed forces on the border with Israel has nothing to do with the Islamic State and everything to do with the Islamic Republic’s ideological desire to threaten the Jewish state.

But what about Turkey? Historically, Turkish-Syrian relations have been tense. Two decades ago, the two countries almost went to war over Hafez al-Assad—the father of Syria’s current leader—providing safe-haven to the Kurdistan Workers Party (PKK), a Kurdish group fighting for a homeland in southeastern Turkey. But, as part of his quest to reset relations with his neighbors in the early 2000s, Turkey’s leader Recep Tayyip Erdogan became one of Assad’s biggest boosters. Prior to the outbreak of civil war in Syria, the two leaders vacationed together on Turkey’s Mediterranean coast, even as Erdogan told Israeli officials he was too busy to meet.