According to officials familiar with the situation, President Obama has ordered the Pentagon to begin conducting military strikes against the leadership of the al–Qaeda-linked Nusra Front, a major rebel faction operating within Syria.

The Nusra Front holds materially the entire Idlib Province, and also has significant territory within neighboring Aleppo Province, including in Aleppo itself. The Islamist group is closely aligned with several US-armed rebel factions, which has long kept the US from launching attacks on them.

The US has at time expressed concern about Nusra’s growing influence, but its reticence to target them cannot be understated. Indeed, the Obama Administration has spent much of the past two months railing against the Russian government for conducting airstrikes against Nusra targets.

Though Nusra has never been a party to any of the US-Russia-brokered ceasefires in Syria, the group’s close ties with several US-armed groups has complicated matters greatly, as often they share bases of operations, meaning attacks on Nusra Front bases also target US-backed groups.

When the US first began bombing Syria, they did attack some Nusra targets, but invented the fictional “Khorasan” faction of al-Qaeda, which they claimed was distinct, to justify the attacks. The attacks were harshly criticized by rebels, and stopped almost immediately, with the US shifting its focus to ISIS.

Attacking Nusra has been seen as problematic for parts of the US government, notably the State Department and CIA, who believe that, as they are one of the few rebel groups successful at fighting the Assad government, they ought to leave them alone for the sake of eventually imposing regime change, even if it means that regime change is heavily al-Qaeda influenced.