The overwhelming majority of Syrian air defense systems that responded to last weekend's coalition strikes did so only after all 105 of the guided missiles had already successfully struck their targets.

According to U.S. government sources with knowledge of the April 14 operation who spoke to The Daily Beast , Syrian air defense crews managed to launch just two interceptor missiles while the coalition strikes were ongoing, both of which failed to strike anything incoming. The sources requested anonymity to discuss the details of a recent military operation.

The feeble air defence effort contrasts starkly to the ludicrous claims of success made by Syria’s ally, Russia. In the aftermath of the strike, the Russian ministry of defence claimed that Syrian forces were successful in intercepting some 70 percent of the sophisticated standoff-range, low-flying Western guided munitions used in the strike despite using Soviet-era systems.

Russian state media even carried reports of celebrations in Damascus on Saturday morning over what the regime touted as a highly successful air defense effort.

In reality, Syrian forces fired 38 of the 40 interceptor missiles used only after the coalition's guided missiles had struck their targets, which included chemical weapons storage and manufacturing facilities near Homs and outside Damascus. Some of the Syrian launches were captured on amateur video footage.

The exact sequencing of the Syrian response is unclear, but the Pentagon explained that the guided missiles used in the strikes were designed to strike within minutes of 4:00 a.m. local time in Syria on Saturday morning.

"All weapons hit their targets at very close to the designated time on target, of about 4:00 a.m. in Syria," Lt. Gen. Kenneth F. McKenzie noted in a press briefing on Saturday. "All of our missiles impacted within a minute or two of that time," McKenzie added. Earlier in the briefing, he described central Damascus, where the strikes destroyed three buildings, as "one of the most heavily defended airspace areas in the world."

The Russian ministry of defense claimed, with a different total count of the number of missiles fired, that Syria successfully shot down 71 out of 103 missiles. In response to the Russian claims about the performance of its ally's air defenses, the Pentagon has countered by noting, on the record, that none of the U.S., British, or French missiles in the strike were intercepted. McKenzie also confirmed on Saturday that none of Russia's advanced S-400 Triumf or S-300 surface-to-air missiles reacted to the strikes.

It is hardly surprising that Syria's late-Cold War-era air defense systems didn't fare too well against advanced low-observable and maneuverable standoff weapons like the U.S. Joint Air-to-Surface Standoff Missile-Extended Range (JASSM-ER).

U.S. JASSM-ER and Tomahawk land-attack cruise missiles, French SCALP, and British Storm Shadow cruise missiles are designed to pose a challenge to adversary interceptors. Air-breathing long-range cruise missiles, because of their ability to fly low and generate a low heat signature in flight, are far from simple for enemy radars to acquire early enough in flight to successfully cue interceptors.

These difficulties even remain a challenge for U.S. missile defense systems and cruise missile defense is expected to feature prominently in the Trump administration's upcoming Missile Defense Review.

Looking at the chronology of Saturday's strikes and the targets that were ultimately struck, it's striking that the coalition did not assign any of its 105 guided missiles to a suppression of enemy air defense mission; the decision suggests that coalition planners were confident that these weapons could penetrate Syrian airspace successfully.

Syria's decision to launch its interceptors after the coalition missiles had already struck may have been driven by a range of factors. Given that the regime seized on the Russian claimed of successful intercepts and used it for internal propaganda ends, it’s possible that setting off a concerted launch after the strikes would have given onlookers near Homs and Damascus the impression that the regime was fighting back, even as the coalition had in reality struck the targets it wanted to.

The performance of Syrian air defenses during last week's strike also may help explain false reports of additional strikes on Monday evening, which were sparked by Syrian forces launching interceptor missiles near Homs.

Syrian state media, after first reporting that regime forces had successfully intercepted missiles inbound for the Shayrat airbase near Homs, later clarified on Tuesday that a false alarm led to the launches.

It's possible that in an acknowledgement of their remarkably poor performance on Saturday, the Syrian military was conducting a responsiveness drill to ensure better reactivity against future strikes. Alternatively, a simpler explanation might be that air defense crews were left skittish after Saturday.

Curiously, Syrian state media also attributed the false alarm launches on Monday to a "joint electronic attack," later going on to add that Russian experts had addressed the issue.

While electronic warfare assets can confuse and overwhelm radars designed to cue air defenses, the Pentagon has not discussed the use of such countermeasures during either Saturday's strikes or in general in Syria.

U.S. EA-6B aircraft accompanied B-1 bombers during the strikes, suggesting that the Pentagon may have seen a need to suppress the more advanced Russian air defenses in Syria—even at standoff ranges. A Pentagon spokesperson, however, denied any U.S. military activity near Homs on Monday.

The implications of the poor performance of Syrian air defenses during Saturday's strike are important for potential future strikes. The United States and its allies may perceive the costs of limited strikes to be more tolerable if cruise missiles can be used against the Syrian regime with impunity. These perceptions could extend far beyond Syria and inform U.S. decision-making with regard to other states with similar air defense capabilities.

The strong performance of the coalition's guided missiles this weekend, however, does not suggest that an air campaign involving fighters and bombers over Syrian airspace is realistic. Both Syria's older air defenses and Russia's systems will continue to pose a threat to aircraft.