Tom Vanden Brook

USA TODAY

WASHINGTON — U.S. special operations forces will be needed on the ground in Syria to make the expanded air war President Obama has ordered there more effective, a senior Air Force commander told USA TODAY.

The spy planes flying missions over Iraq and Syria can develop a list of potential Islamic State targets, said the commander who spoke on condition of anonymity to describe what the war might look like. But it's "absolutely crucial that pilots are talking to an American on the ground" who can verify that the target is legitimate.

The CIA said Thursday evening that a new intelligence assessment estimates the Islamic State can muster between 20,000 and 31,500 fighters across Iraq and Syria, up from a previous figure of 10,000. CIA spokesman Ryan Trapani said the new assessment is based on a review of intelligence reports from May to August, the Associated Press reported.

Obama has said he is not sending traditional ground combat troops to Iraq or Syria. However, there will be teams of about 12 American troops advising and assisting Iraqi forces.

Syria's air defense network, the officer said, will probably not be a major concern for U.S. pilots, because the Syrian weapons are concentrated near the capital of Damascus and the border of Israel. ISIL forces would probably not be able to operate sophisticated surface-to-air missile systems that require extensive training to operate.

A close parallel for the effort against ISIL, the officer said, could be the early stages of the U.S. war that toppled the Taliban in Afghanistan in late 2001. Small groups of U.S. special operators, sometimes on horseback, worked with fighters from the Northern Alliance to locate and destroy Taliban targets.

That comparison applies in Iraq where competent indigenous commandos and Kurdish peshmerga fighters can take advantage of bombing runs, said Michael O'Hanlon, a military analyst at the Brookings Institution. In Syria, it will take time to train and work with reliable allies.

"We don't have that now in Syria," O'Hanlon said. "So this model works for Iraq soon, but not for Syria until 2015, 2016."

Meantime, there may be opportunities to attack targets in Syria, such as ISIL leaders, but a sustained campaign there is unlikely for a few years, O'Hanlon said.

"You have to have local allies who can protect you before you do that," O'Hanlon said.

The officer, who has not been involved in planning the campaign, stressed the need for U.S. forces on the ground to pinpoint legitimate targets to avoid civilian casualties and to avoid being used by indigenous forces to settle scores.

Obama, in his address from the White House, said no U.S. combat troops would be on the ground in either country. Rear Adm. John Kirby, the Pentagon press secretary, repeated that pledge Thursday, saying there is no intention that the 1,000 U.S. troops in Iraq will engage in combat.

The Pentagon's expanded authority to bomb Islamic State terrorists in Iraq and Syria appears to include targeting its leadership. Kirby said the mission includes going after the Islamic State's "command and control."

That seems to indicate planners will be able to target those who head the terror group, including Abu Bakr al-Bagdhdadi, who has called himself the leader of the group. During the Iraq war, he had been a U.S. prisoner but was released.

Kirby suggested but did not state that the Islamic State's leadership would be in the cross hairs of U.S. warplanes. Destroying the Islamic State's capabilities, Kirby said, includes "disrupting their ability to command and control, and to leader their own forces."

Meanwhile, U.S. commandos have been in Syria as recently as July. They took part in a failed attempt to rescue American hostages held by ISIL terrorists. It's not clear if the White House defines them as "combat troops."

When Taliban fighters massed near Mazar e Sharif in 2001, U.S. air strikes "clobbered them," the officer said, and the Northern Alliance moved on to rout the Taliban quickly.

Airstrikes will not be enough to destroy ISIL militants, the officer said. That will require competent ground forces — Iraqi or Syrian — who can take advantage of the edge that strikes from the air. Airstrikes can halt ISIL momentum, and tilt the playing field toward force aligned with U.S. interests, the officer said.

The commander also downplayed the effectiveness of Syrian air defenses, at least in its eastern desert region. The most sophisticated anti-aircraft weapons are clustered around the capital of Damascus and Syria's border with Israel.