CAIRO — President Trump’s decision to abruptly withdraw American forces fighting the Islamic State in Syria has opened questions about American military plans in neighboring Iraq, where the militant group continues to stage sporadic attacks despite losing all of the territory it once controlled.

Opponents and supporters of U.S. troops in Iraq have been quietly weighing the prospect of another American pullout from a country that has seen varying levels of U.S. military presence since the invasion that toppled Saddam Hussein in 2003.

Trump has given no signals on plans for the military in Iraq. But the U.S. armed forces are much more enmeshed in Iraq’s affairs — including as partners with elite Iraqi military units — than in Syria. U.S. units in Syria operated with Kurdish and Arab allies in territories largely outside government control.

Any sweeping Pentagon disengagement would carry the potential for major changes in how Iraq’s security forces are run and in their capacities to face any possible resurgence by the Islamic State or other threats.

As in Syria, the Islamic State in Iraq has been driven from its strongholds. But in contrast to Syria, the influence of Iranian-
allied groups runs even deeper through Iraq’s political and security arenas — an argument raised by supporters of the U.S. military presence in Iraq.

“There is deep worry among Iraqi military officers, who see the Pentagon as stable but the White House as unpredictable,” said a Western diplomat based in Baghdad whose country is involved in the U.S.-led coalition opposing the Islamic State. The diplomat spoke on the condition of anonymity to discuss private conversations with Iraqi officials.

Other soldiers of the Iraqi Emergency Response Brigade march in the parade in Baghdad on Dec. 10, 2018. (Murtaja Lateef/EPA-EFE/Shutterstock)

“ISIS has been defeated in Iraq as well, why don’t you withdraw your forces then?” Qais al-Khazali, the influential commander of the Iranian-backed Shiite militia Asaib Ahl al-Haq, wrote on Twitter. “Unless there is another reason you are keeping them here.”

Analysts and some Iraqi officials said Washington’s surprise decision on Syria will further empower pro-Iranian figures to press for a withdrawal of U.S. forces from Iraq. Backers of the U.S. presence warn that a pullout could imperil hard-won gains against the Islamic State while weakening Iraq’s security forces, which rely heavily on U.S. training and other support.

Critically, Trump’s decision on Syria suggests that his administration views the fight against the Islamic State in purely military terms.

“Iraq should indeed be worried, mainly because the political solution to tackle the roots of ISIS has not been addressed,” said Renad Mansour, an Iraq expert with the Chatham House think tank in London. “In parts of Iraq, where state institutions remain a distant reality, ISIS is already planning a resurgence.”

Since Iraq declared military victory over the Islamic State last December, the presence of U.S. forces in the country has emerged as a wedge issue. In elections in May, political movements hostile to U.S. involvement in Iraq won more than 100 seats in the 329-seat parliament.

Some have called for the total withdrawal of American forces, while others indicated that they would be supportive of keeping a small number of U.S. military advisers. American officials have said a U.S. military alliance with Iraqi forces is needed to avoid a repeat of the near-total collapse of Iraq’s security forces during a 2014 blitz by the Islamic State, which included the militants’ gaining control of Mosul, the largest city in Iraq’s north.

In November, the Defense Department’s inspector general issued a report with the sobering assessment that Iraqi forces would need “years, if not decades,” to become self-reliant.

“Systemic weaknesses remain, many of which are the same deficiencies that enabled the rise of ISIS in 2014,” the report said.

From its headquarters in Baghdad’s fortified Green Zone, the U.S.-led military coalition has directed the four-year battle to oust the Islamic State from the nearly one-third of Iraqi territory it controlled at its peak.

Some 5,200 U.S. troops remain in Iraq, based in Baghdad and outposts in the country’s north and west.

Clearing Mosul of the militants took Iraqi troops nine months, the longest and bloodiest of several fights since 2014. U.S. military personnel worked closely with Iraqi ground forces, helping to coordinate troop movements and airstrikes.

Today, Americans have transitioned from advising Iraqi forces in active combat to the much more delicate and intricate work of counterterrorism operations guided by intelligence gathering — an area of acute deficiency the Defense Department identified in Iraq’s military capabilities.

U.S. forces are also supporting Iraqi military units that patrol and secure the country’s eastern border with Syria against possible Islamic State infiltration.

No Iraqi force has benefited more from the partnership with the United States than the Counter Terrorism Service, or CTS, which was created and trained by the United States after the 2003 invasion.

The service is credited with doing the vast majority of the fighting to oust the Islamic State from Iraq. But it is only now beginning to recuperate from the losses it suffered during the campaign and return to its original mission of targeted and preemptive operations against suspected militant cells, officers said.

The Islamic State has gone underground in Iraq, unable to gain any foothold in large, urban population centers. The militants are instead focusing on reconstituting in rural areas in five Sunni-majority provinces, Lt. Gen. Abdulwahab al-Saidi, the commander of the CTS, said in a recent interview.

“The operations they are doing are expected,” he said. “Some limited attacks that are nothing compared to their attacks in 2014.”

Any U.S. troop drawdown or loss of U.S. support for Iraq’s military would be devastating, other CTS officers said. Some say the drawdown of U.S. forces in Iraq in 2011 helped create conditions for the Islamic State to emerge. Trump derided that decision by the Obama administration in a tweet seven years ago.

But the CTS officers pointed at significant differences between the U.S. mission in Syria and Iraq.

American forces are in Iraq at the invitation of the Iraqi government under a 2008 agreement. U.S. troops are present in Syria without permission from the government of President Bashar al-Assad.

“Their withdrawal from Syria might actually mean increasing their presence here in order to watch Syria,” said a CTS brigadier general, who spoke on the condition of anonymity because he was not authorized to speak to the media. “No matter what, the U.S. will not allow ISIS to get stronger in Syria.”

Naeem al-Aboudi, a newly elected lawmaker from a pro-Iranian faction, said Trump’s decision will have no military impact on Iraq because Shiite militias have taken on a prominent role in securing Iraq’s borders.

The impact, he said, is on perceptions of the United States in Iraq.

“It should be a lesson for Iraq not to depend or trust [the United States], because they can leave in a second,” he said. “They are not the right ally. They always put their interests ahead, even if that means destroying their allies. Iraq shouldn’t consider them partners or depend on them.”

Mustafa Salim in Baghdad contributed to this report.