---

HMEIMIM AIR BASE, Syria—North from Syria, along the borders of Eastern Europe and rounding the Arctic Circle to the east, Russia has built a ring of air defenses that threaten the reach of the U.S. military, forcing Washington to rethink its place as the world’s undisputed air power.

Russia’s S-400 antiaircraft missile system, a nettlesome and potentially deadly aerial shield, is changing the calculus of the U.S. and its allies in potential hot spots, beginning with its deployment in Syria.

Radar employed by the S-400, which Russia claims can detect the latest stealth aircraft, casts a net around western Syria that stretches from Turkey to the Mediterranean Sea to Israel.

While it hasn’t been tested in battle, S-400 radar tracking has shooed away aircraft of the U.S.-led coalition in Syria “as soon as they see on their electronic indicators that they are being watched,” Lt. Gen. Viktor Gumyonny, commander of Russia’s air-defense forces, told a TV interviewer.

Russia’s hybrid warfare tactics against the West, including election meddling and online disinformation campaigns, have drawn the most attention from lawmakers and the U.S. government. Proliferation of the S-400 system demonstrates how Russia is also investing heavily in traditional military firepower.

---