Tuesday’s drone strike on Moscow further demonstrated the spread of the war in Ukraine to the Russian capital, putting a spotlight on the city’s air defenses and the Kremlin’s attempts to adapt to a new kind of conflict.
Since the 1980s, Moscow has been ringed by a complex air defense system known as Amur, which was designed to protect the capital from intercontinental ballistic missiles and nuclear bombers, a threat far different from the reality of Russia’s modern war against Ukraine.
Ukraine has denied responsibility for Tuesday’s drone attack and another this month that targeted the Kremlin, but such assaults have been increasing in frequency in Russian territory. This has forced Russia to adopt its defense systems to counter a kind of ordnance that is less lethal but much more numerous.
In January, Russia began stationing new military hardware around Moscow without official explanation, including on top of prominent buildings such as the Defense Ministry. Military experts identified the weapons as the S-400, Russia’s most sophisticated surface-to-air missile system, and the Pantsir S-1, which in its most common form is a truck carrying a relatively simple antiaircraft missile launcher.
Pantsir missiles downed five of the eight drones that attacked Moscow on Tuesday morning, according to the Defense Ministry. A video posted on social media on Tuesday and verified by The New York Times showed a Pantsir system launching a missile on the outskirts of Moscow.
The other three drones, according to the Defense Ministry, were disabled by what it called “radio-electronic warfare.” The ministry did not provide details, but starting in 2016 it has been installing an electronic jamming system known as Pole-21 on satellite towers. These systems block satellite navigation signals, causing drones and other electronically guided weapons to lose control.
As a result, Russian officials — including President Vladimir V. Putin — have tried to frame the attack on the capital as a triumph for Russian defenses.
“It’s clear what needs to be done to increase the density of the capital’s air defense systems,” Mr. Putin said in response to the attack. “And we will do just that.”
One potential issue: The effectiveness of the Pantsir and Pole systems declines greatly in densely populated areas saturated with satellite data, said Ruslan Pukhov, the director of the Moscow-based security research group CAST. To effectively counter drone attacks, he said, the Russian military must try to disable them before they reach city limits — a difficult task given the size of the country.
Defending airspace in urban areas is also more difficult than near the front lines, where most aircraft will be military. Around cities, soldiers have to track civilian aircraft, like airplanes and helicopters, while at the same time looking for radar reflections of much smaller aircraft, like unmanned drones.
“Previously, air defense systems near cities would tune out anything smaller than a helicopter,” said Ian Williams of the Missile Defense Project at the Center for Strategic and International Studies, a Washington think tank. “Small drones may have a radar return the size of a goose, so if you tune your radars to look for enemy drones you’ll also see a lot of birds.”
The Pantsir air-defense vehicles seen around Moscow came into service with the Russian Army in 2003, according to C.S.I.S., and have since been upgraded. Armed with short-range infrared-seeking missiles and a 30-millimeter gun directed by radar, the Pantsir was built to accompany mechanized forces like a tank column, Mr. Williams said, providing a “bubble” of protection as the convoy moves along.
They were designed and built before small drones became a major threat on the battlefield, Mr. Williams said, and although they do have some ability to shoot drones down, that is not what they were optimized to do. Attackers can also use terrain to mask the approach of low-flying aircraft, like drones, he added.
Those responsible for Tuesday’s attack, he said, appeared to be “exploiting the limitations of the Pantsir and other air-defense systems around Moscow.”
Oleg Matsnev and Riley Mellen contributed reporting.