So Many Airstrikes, Still So Many ISIS Jihadists

More than 1,000 foreign fighters are streaming into Syria each month, a rate that has so far been unchanged by airstrikes against the Islamic State and efforts by other countries to stem the flow of departures, according to U.S. intelligence and counterterrorism officials.

The magnitude of the ongoing migration suggests that the U.S.-led air campaign has neither deterred significant numbers of militants from traveling to the region nor triggered a spike in the rate of travel among Muslim populations inflamed by American intervention.

"The flow of fighters making their way to Syria remains constant, so the overall number continues to rise," a U.S. intelligence official said. U.S. officials cautioned, however, that there is a lag in the intelligence being examined by the CIA and other spy agencies, meaning it could be weeks before a change becomes apparent.