Jim Michaels

USA TODAY

Syrian leader Bashar Assad is increasingly relying on a network of local militias and foreign fighters to defend his regime as his regular army has been eroded by defections and heavy casualties after three years of war.

His ability to rely on thousands of irregular forces, including local militias and the militant group Hezbollah, has been a factor in Assad's ability to stabilize his position in recent months, though analysts and U.S. officials say neither side is capable of outright victory.

The local militias have grown to about 60,000 fighters, according to David Kilcullen, a counterinsurgency expert who testified before the Senate Foreign Relations Committee last week.

Assad's regime has built the local militias with the assistance of Iranian advisers under the umbrella of the National Defense Force.

The strategy of relying increasingly on irregular forces has also diversified Assad's support, providing him with armed forces more loyal than his army, which has been hurt by defections.

"Much of the Syrian army is no more," said a senior Israeli military official, who asked not to be named because he was not authorized to speak publicly. The militias allow Assad to hold terrain, freeing up his army to conduct more concentrated offensives.

"The Syrian army is clearly incapable of defending the regime," said Yossi Alpher, an Israeli security analyst.

But analysts and U.S. officials acknowledge that neither side has a decisive advantage despite the regime's recent progress. Rebel groups have also launched some of their own offensives, with notable successes.

"The battlefield situation ebbs and flows," said Anne Patterson, a State Department official, testifying recently before the Senate Foreign Relations Committee.

In addition to local militias, Assad is also relying heavily on about 5,000 Hezbollah fighters, which have proven more effective than conventional forces in battling rebels in towns and villages

"These are people who have a lot of experience in urban irregular warfare," Kilcullen said. The Lebanese-based Shiite guerrilla group has had years of experience fighting Israeli forces.

Conventional forces, meanwhile, can be called on when artillery and air support is needed or to concentrate forces during a regime offensive against an opposition stronghold.

"It's still too close to call but clearly the situation is much better for Bashar than it was a year ago," said Eyal Sisser, a professor at Tel Aviv University.

The problem for Washington is that even the rebel successes are not necessarily good news for U.S. policy. Many of the recent successful operations against regime forces have been conducted by extremist groups.

"The momentum has shifted away from the moderates … to the benefit of these more extremist groups," said Chris Chivvis, an analyst at Rand Corp.

Syria has become a magnet for Islamist extremists. The intelligence community estimates there are 23,000 extremist fighters in Syria, including more than 7,000 foreign fighters, Patterson said.

The Russians and Iranians continue to pump arms and equipment to support Assad's regime.

But the United States has struggled to support the opposition, partly because of the difficulty of identifying reliable groups and then getting supplies to them.

"Even al-Qaeda is splintered," the Israeli official said.

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