Rebel fighters take positions inside a room as they aim their weapons through holes in a wall in the old city of Aleppo near the frontline against forces loyal to Syria's President Bashar al-Assad on December 28, 2014. (Jalal Al-Mamo/Reuters)

The Syrian regime has intensified efforts to reverse substantial manpower losses to its military with large-scale mobilizations of reservists as well as sweeping arrest campaigns and new regulations to stop desertions and draft-dodging.

The measures have been imposed in recent months because of soaring casualties among forces loyal to President Bashar al-Assad, as well as apparent increases in desertions and evasions of compulsory military service, analysts say. Some speculate that the moves also could be part of stepped-up military efforts to win more ground from rebels in anticipation of possible peace talks, which Russia has attempted to restart to end nearly four years of conflict.

But the regime’s measures have added to already simmering anger among its support base over battlefield deaths during the conflict. The anger may be triggering a backlash that in turn could undermine Assad’s war aims, Syrians and analysts say.

“These things have obviously angered core constituents, and they show just how desperate the regime is to come up with warm bodies to fill the ranks of the Syrian Arab Army,” said Andrew Tabler, a senior fellow and Syria expert at the Washington Institute for Near East Policy.

In October, the regime stepped up activations of reserve forces. Tens of thousands of reservists have been called up, and soldiers and militiamen have erected scores of checkpoints and increased raids on cafes and homes to apprehend those reservists who refuse to comply. Similar measures increasingly target those who avoid regular military service, a compulsory 18-month period for all men who are 18 and older.

In recent weeks, the regime also began upping threats to dismiss and fine state employees who fail to fulfill military obligations, according to Syrian news Web sites and activists. In addition, they say, new restrictions imposed this fall have made it all but impossible for men in their 20s to leave the country.

Since the start of the uprising in 2011, Syrian authorities have used arrests and intimidation to halt desertions, defections and evasion of military service — but not to the extent seen recently, Syrians and analysts say. Men who are dragooned into the army appear to be deserting in larger numbers, they say, and the government’s crackdown is driving many of these men as well as more of the large number of draft-evaders to go into hiding or flee abroad.

“I can’t go back. All these things would make it certain that I’d be forced into the military,” said Mustafa, 25, a Syrian from Damascus who fled to Lebanon in September because of the new measures. Citing safety concerns, he asked that only his first name be used.

Joseph, a 34-year-old Christian from Damascus, learned two weeks ago that his name was on a list of thousands of people who would soon be activated for reserve duty. Having completed his compulsory military service in 2009, he wants to flee Syria.

“Of course I don’t want to return to the military,” Joseph said by telephone from the capital. He also requested that only his first name be used.

A report issued this month by the Institute for the Study of War says the number of soldiers in the Syrian military has fallen by more than half since the start of the conflict, from roughly 325,000 to 150,000, because of casualties, defections and desertions. Combat fatalities alone have surpassed 44,000, according to the report, which used data from Syrian activists, monitoring groups and media reports.

Christopher Kozak, a Syria analyst at the institute who wrote the report, said in an e-mail that reservist mobilizations and efforts to stop desertions appear to be partly related to the departure in recent months of pro-regime militiamen. Scores of these largely Shiite fighters, who come from Iraq, Iran, Afghanistan and Lebanon’s Hezbollah movement, left for Iraq in the summer summer to counter an offensive by the Islamic State, the extremist Sunni group.

Iranian fighters in particular have been crucial in helping the Syrian regime restructure its forces. One such effort was the founding of the National Defense Force, a militia composed of paid volunteers. The foreign fighters helped the Assad regime win back strategic territory from rebels.

Kozak wrote that these supplemental militias “are no longer sufficient to meet the regime’s projected needs — spurring the regime to reinvigorate its conscription efforts” in the military.

Imad Salamey, a politics professor at the Lebanese American University, said that efforts to boost numbers in the military are partly driven by concern that Assad’s allies, Iran and Russia, appear increasingly interested in a negotiated settlement to the Syrian civil war. In recent weeks, Russia, with Iranian backing, has engaged in diplomatic efforts to restart the Geneva peace talks that collapsed in February.

“There is rising urgency in these countries for a settlement to the conflict and the regime senses this, so it’s trying to win as much ground as possible to strengthen its negotiating position,” he said.

Yezid Sayigh, a Syria expert and senior associate at the Carnegie Middle East Center in Beirut, said economic crises in Iran and Russia because of falling oil prices could affect their support for the Assad regime, which until now has prevented its collapse. “The question for me really is whether Iran and Russia are going to push the regime harder to engage in diplomatic efforts,” he said.

He added that a worsening problem for the regime is anger among its supporters over mounting casualties. Rare protests over the issue have been held by the minority Alawite population, which is the backbone of the Assad regime’s forces.

Other minority groups, such as Syria’s Druze community, also show signs of dissent. In their villages in southern Syria, most Druze families have refused to allow their sons to join the military. In an incident earlier this month, Druze villagers kidnapped regime intelligence officers in an attempt to free a man who was apprehended for refusing to serve in the military.

“The people are turning on the regime here because they don’t want their children to die in this war. They don’t see the point of this war,” said Qusay, 22, a resident of the mostly Druze city of Suwayda and engineering student at Damascus University. He also asked that only his first name be used.

“If the regime tries to push us to serve, there will be a fight.”

Sam Alrefaie contributed to this report.