The specially designed missiles use sharp blades and blunt force, rather than explosive warheads, to kill terrorist leaders.
U.S. Special Operations forces, with no fanfare, killed a top Qaeda leader in northwest Syria in an unusual drone strike nearly two weeks ago.
They used a secretive weapon — a so-called Ninja Hellfire missile on which the explosive warhead is replaced by long blades to crush or slice its victim while minimizing risks to any civilians nearby. It was the second time in three months that American commandos have killed a senior Qaeda leader in northwest Syria with these specially designed missiles.
The strike illustrated the complexities of carrying out operations against terrorist groups in a part of the world where the United States and Russia have been warily pursuing their own objectives and occasionally coming into conflict.
The recent ramming of an American ground patrol by a Russian armored vehicle escalated tensions between the two rival powers in northeast Syria. The clash prompted the Pentagon last week to dispatch Bradley fighting vehicles and more fighter jet patrols to reinforce the more than 500 American troops helping stamp out remnants of the Islamic State there.
But in an opposite corner of the country, where the United States has no troops on the ground, the military’s secretive Joint Special Operations Command, with help from the C.I.A., is carrying out a shadow war against a different terrorist threat — a small but virulent Al Qaeda affiliate — that American officials say is plotting attacks against the West.
The Pentagon will not say much about the latest Reaper drone strike in northwest Syria. Maj. Beth Riordan, a spokeswoman for the U.S. Central Command, confirmed a military strike near Idlib on Sept. 14 against the Qaeda affiliate in Syria, but offered no details.
Other American military and counterterrorism officials, as well as the Syrian Observatory for Human Rights, said that the Hellfire missile strike killed Sayyaf al-Tunsi, a Tunisian who was a senior planner of Qaeda attacks against the West, including the United States. U.S. military officials said Mr. al-Tunsi’s death would disrupt operations of the Qaeda affiliate, called Hurras al-Din.
On Thursday, the government’s top counterterrorism official hinted at the clandestine campaign to destroy the group’s leadership, without offering specific details, most of which remain classified.
“In Syria, Hurras al-Din — a group made up of several Qaeda veterans — has suffered successive losses of key leaders and operatives, which, along with conflicts with other violent extremist factions and the erosion of its safe haven in Idlib Province, has stunted the group’s growth,” Christopher Miller, the director of the National Counterterrorism Center, told the Senate Homeland Security and Governmental Affairs Committee.
The Qaeda leaders in Syria have sought to operate in urban areas, calculating that American forces will be wary of carrying out missile strikes that could harm civilians.
But the modified Hellfire missile carries an inert warhead. Instead of exploding, it hurls about 100 pounds of metal through the top of a target’s vehicle. If the high-velocity projectile does not kill the target, the missile’s other feature almost certainly does: six long blades tucked inside, which deploy seconds before impact to slice up anything in its path.
The Hellfire variant, known as the R9X, was initially developed nearly a decade ago under pressure from President Barack Obama to reduce civilian casualties and property damage in the United States’ long-running wars on terrorism in far-flung hot spots such as Afghanistan, Pakistan, Iraq, Syria, Somalia and Yemen.
The weapon has been used perhaps a half-dozen times in recent years, American officials said, typically when a senior terrorist leader has been situated but other weapons would risk killing nearby civilians.
Conventional Hellfire missiles, with an explosive warhead of about 20 pounds, are often used against groups of individuals or a so-called high-value target who is meeting with other militants. But when Special Operations forces are hunting a lone leader, the R9X, called the Ninja by commandos, is now often the weapon of choice.
American Special Operations forces used a R9X missile in June to kill Khaled al-Aruri, the de facto leader of the Qaeda branch in Syria. He was a Qaeda veteran whose jihadist career dates to the 1990s. American officials confirmed the use of the unusual missile in two earlier instances, one by the C.I.A. in northwest Syria and one by the Joint Special Operations Command in Yemen.
The center of the latest drone strikes is Idlib Province, whose population has ballooned to more than three million people during Syria’s civil war. It contains a witch’s brew of violent Islamic extremist groups, dominated by the Qaeda-linked organization Hayat Tahrir al-Sham, formerly the Nusra Front. Syrian military forces, backed by Iranian and Russian firepower, have targeted the group.
Hurras al-Din emerged in early 2018 after several factions broke away from the Nusra Front, which at least publicly has since distanced itself from Al Qaeda’s overall leadership in Pakistan. Hurras al-Din is the successor to the Khorasan Group, a small but dangerous organization of hardened senior Qaeda operatives that Ayman al-Zawahri, Al Qaeda’s leader, sent to Syria to plot attacks against the West.
The Khorasan Group was effectively wiped out by a series of American airstrikes several years ago. But with as many as 2,000 fighters, including seasoned leaders from Jordan and Egypt, Hurras al-Din is much larger and has operated in areas where Russian air defenses, at least until recently, have largely shielded its members from American airstrikes and the persistent stare of American surveillance planes.
Moscow dispatched military aid and advisers to Syria in late 2015 to support the beleaguered government of President Bashar al-Assad.
“The group remains committed to preparing for external attacks despite its current focus on targeting Syrian forces,” a United Nations counterterrorism assessment concluded in July.
Hurras al-Din is considered so dangerous that as recently as this summer, the Pentagon took the unusual step of using a special hotline to Russian commanders in Syria to allow the Special Operations forces to conduct uncontested airstrikes against the Qaeda leaders. Previous strikes have also attacked training camps in Aleppo and Idlib Provinces.
These are rare attacks west of the unofficial dividing line between American forces to the east of the Euphrates River, and Russian and Syrian government troops to the west of the river.
“As for the Russians, we do deconflict flights in northwest Syria,” said one senior American military official. “While they don’t particularly like us being there, most of the time they don’t object.”
Terrorism analysts say internecine tensions between the two Qaeda-related groups in Syria have boiled over in recent months, posing another problem for Hurras al-Din.
“As of late June, battlefield conflicts between Hurras al-Din and the Nusra Front continued to escalate, prompting Al Qaeda to issue a public statement condemning the fighting,” Mr. Miller, the counterterrorism chief, said on Thursday.
Terrorism analysts say these tensions and the increasing American drone strikes are putting more pressure on Hurras al-Din. “Al Qaeda in Syria is in a hard spot,” said Aaron Y. Zelin, a terrorism scholar at the Washington Institute for Near East Policy. “They don’t have much room to maneuver.”
But other analysts point to reports that some Qaeda operatives may have fled to other parts of Syria or across the border into Lebanon, and could continue plotting from there.
“We’re on borrowed time with Al Qaeda in Idlib,” said Jennifer Cafarella, a national security fellow at the Institute for the Study of War in Washington.