Across the group’s territory in Iraq and Syria, a breakdown of services and deteriorating living conditions call into question its ability to govern and the sustainability of its ambition.
The strikes were probably aimed at Iranian shipments of weapons to Hezbollah, analysts say.
The country could soon be divided almost entirely between extremists and Assad regime forces, leaving moderates without territory and Washington without allies, rebels and analysts say.
The strikes may have far-reaching effects for the longer-term strategy of strengthening moderate fighters.
Fighters from Jabhat al-Nusra are closing in on moderate Syrian rebels who were routed over the weekend.
U.S. strategy suffered a major setback, ending hopes of readily finding Syrian partners for the fight.
The Assad regime accused Turkey of violating Syrian sovereignty after foreign fighters crossed the border.
The divergence of views between the two countries over how to handle the Islamic State threat in Syria has laid bare the fault lines of an increasingly fragile, but still strategically vital, diplomatic relationship.
Syrian rebels and Iraqi Kurdish fighters have mobilized to aid the besieged town near Turkey’s border.
A brazen but ultimately failed effort to kidnap a Syrian rebel leader in broad daylight raises troubling questions about Islamic State’s growing reach into Turkey.