Michael G. Vickers served as assistant secretary of defense for special operations, low-intensity conflict and interdependent capabilities and undersecretary of defense for intelligence during the Bush and Obama administrations.

Based on recent statements by several senior administration officials, President Trump’s Syria policy now focuses exclusively, in cooperation with Russia, on defeating the Islamic State. President Barack Obama’s goal of removing Syrian dictator Bashar al-Assad from power is no longer a U.S. foreign policy objective.

Acquiescing to Assad remaining in power, and ending support for the Syrian moderate opposition, would strengthen our adversaries, further convince allies that the Trump administration places Russian interests above our own, enable Iran to consolidate strategic gains, increase the global jihadist threat to the United States — and make a stable Middle East that much harder to achieve.

Abandoning the goal of removing Assad from power will place the United States on the side of not only the barbaric Syrian regime, which has American blood on its hands dating to the early 1980s, but also Iran, Hezbollah and Russia. This is strategic folly.

In the early 1980s, the regime of Hafez al-Assad — the current Syrian dictator’s father — facilitated Iran’s creation of Lebanese Hezbollah, which in short order resulted in the bombing of the U.S. Embassy and Marine Barracks in Beirut and the kidnapping, torture and murder of several U.S. citizens, including William Buckley, the CIA’s Beirut station chief. Before the 9/11 attacks, Hezbollah had taken more American lives than any terrorist group in the world. Two decades later, during the U.S. occupation of Iraq, the Assad regime facilitated the flow of Sunni terrorists to Iraq, resulting in many more American deaths.

Iranian power has grown steadily in the Middle East during the past four decades. Shortly after the 1979 revolution, Iran aligned itself with the Assads, and over time Iran enabled Hezbollah to dominate Lebanon militarily, placing Israel under the constant threat of massive rocket attack. More recently, Iran has supported a Houthi takeover in Yemen, deposing a key U.S. ally in the fight against al-Qaeda, and exerted its influence over the Shiite-dominated government in Baghdad. The civil war in Syria represented our primary opportunity to roll back Iranian power in the Middle East and to sever its primary supply line to Hezbollah. We are squandering that opportunity.

With its 2015 intervention in Syria, Russia has become engaged militarily in the Middle East for the first time in decades. Additionally, in the past three years, Vladimir Putin’s Russia has waged unconventional and conventional war to dismember Ukraine and attacked American democracy. Russian aggression will not cease until it is hit back hard. Stepping up support for the moderate Syrian opposition, providing Ukraine with defensive weapons and countering Russian actions in cyberspace would be great places to start.

The Trump administration’s exclusive focus on the global jihadist threat in Syria is shortsighted, as the civil war and the jihadist threat emanating from Syria are strategically intertwined. One cannot win the latter without winning the former.

The Assad regime’s brutality against its majority Sunni population has been a magnet for international terrorist travel to Syria, and it will continue to serve as a rallying cry for global jihadists. If the United States is viewed as being on the side of the Assad regime, Russia and Iran, we will become even more of a target for jihadists. Elements of the moderate Syrian opposition — there are tens of thousands of them — will no doubt become radicalized by this abandonment, strengthening jihadist ranks.

Defeating global jihadist groups in Syria, and not just displacing them, requires a post-Assad Syrian government with which we can partner for sustained counterterrorism operations. Likewise, rolling back Iranian influence is a precondition of achieving a balance of power favorable to U.S. interests in the Middle East.

Some Americans may think the policy goal of seeking Assad’s removal from power was unachievable without large-scale military intervention, but that is not the case. The Assad regime has been in real peril several times during six years of civil war, and if more U.S. support had been provided to the moderate opposition during the Obama administration, a political transition to a representative Syrian government might have been achieved.

President Ronald Reagan understood the potential of covert proxy wars to alter global power balances. Through stepped-up support for the Afghan mujahideen and other anti-Communist movements, and other, complementary strategic policies, he won the Cold War. It took the Carter and Reagan administrations more than five years to come up with a war-winning strategy (work that I helped to lead as a CIA officer) against the Soviet Union in Afghanistan. The same could be done in Syria today.

The United States faces growing challenges to the international order from Sunni global jihadists and the Iranian regime in the Middle East, from Russia in Europe and from China in East Asia. Making common cause with Russia and Iran in Syria can only lead to the further erosion of U.S. global power.

So a pressing question arises: Why would the Trump administration embrace a Syria policy that serves Russian and Iranian interests and harms American interests? In time, we will learn the answer.