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.