Moscow took a huge risk in the Sea of Japan when an unarmed Russian airborne early warning radar aircraft penetrated South Korea’s internationally recognized airspace.

At first, the Russians said they did not violate South Korea’s airspace. Next, they claimed the intrusion was inadvertent, and was caused by a technical fault, a “malfunction” on their plane’s radar.

Finally, the Russians apologized, expressing “deep regret” over the incident.

The English-language editions of Sputnik and RT (Russia Today) did not report the “malfunction” or the apology. Izvestia said “South Korea’s controversial actions in the skies above the Sea of Japan should be treated as a misunderstanding,” with this statement attributed to a Russian lawmaker.

TASS went on to say that South Korea’s Air Force interfered with Russia’s aircraft that were operating in its Air Defense Identification Zone (ADIZ), an area that is not recognized under international law. But TASS and Izvestia did not discuss the Russian radar plane’s penetration into South Korea’s territorial airspace, generally recognized as 12 miles from the coastline.

The 12-mile limit

The Law of the Sea Convention supports the definition of territorial sea out to a distance of 12 miles, or 22 kilometers, which is also widely accepted in other agreements and in customary international law. Originally, the territorial sea area was fixed at three miles, or 4.8 km, which was based on an historical Dutch notion that this was the outer range a cannon shot could reach from a coastal emplacement in the 18th century.   

The US, which is not a signatory to the Law of the Sea Convention (1982), kept a three-mile limit until 1988 when by Presidential Proclamation the limit was extended to 12 miles. Like South Korea, Japan, China and Russia, the US also claims an ADIZ, which has been in place since 1950. An ADIZ usually extends to areas a country considers vital to its national security.

The question is, why did a Russian radar plane depart from an exercise within South Korea’s ADIZ but outside the country’s 12-mile limit and twice intrude into South Korea’s territorial zone?

Russia was in a joint power projection military air exercise over the Sea of Japan, teamed with China. Russia contributed two Tupolev Tu-95MS “Bear” bombers and one Beriev A-50 “Mainstay” airborne early warning and control aircraft (AEW&C) to the operation.  

The first Beriev A-50 was reportedly seen in 1980 – entering service in the USSR in 1984 – as the Soviet Union’s answer to the American AWACS (Airborne Warning and Control System), the Boeing E-3 Sentry. The E-3 went into service in 1977 and was based on a Boeing 707 commercial jetliner. 

Eyes in the skies

Both the Beriev and the E-3 have large radar domes mounted on the top of the aircraft. In the early phases of both programs, these radar domes rotated to give the mechanically scanned radar all-around coverage. 

The US built the AWACS initially as part of NATO defenses against the USSR. Of the 34 E-3s built, 18 were based in Germany during the Cold War. Thought of as a long-range situational awareness and battle management platform that could channel fighter aircraft to incoming threats, the E-3 gave US and NATO forces eyes deep into Warsaw Pact territory, capable of surveying both airspace and – to a certain extent – ground operations, and from their coverage acted as a force multiplier. 

Later, the E-3 would be used in Operation Desert Storm and other US operations in the Middle East and elsewhere. The US sold E-3s to Saudi Arabia and more updated versions based on the Boeing 767 to Japan. The UK and France also operate E-3s. 

The Russian Beriev A-50 AEW&C has an interesting history. While the aircraft, now being modernized, is in service in Russia, the only foreign customer is India.  But the Indian version – the Beriev A-50EI – is significantly different.

It was the first A-50 – all models based on the Il-76 military transport – with upgraded engines, and its electronics, including a modern, electronically scanned phased array radar called Phalcon, was provided by Israel, in a three-way deal between India, Russia and Israel.

Israel also partnered with Russia and signed a contract to provide the upgraded A-50 with the Phalcon radar to China. That deal fell through after considerable US pressure on Israel. 

China’s first AEW&C aircraft was the ZDK-03 Karakoran Eagle (Y-8J:). The ZDK-03 was equipped with radar from the then-cancelled (1986) British Nimrod AEW program and four ZDK-03 units were sold to Pakistan in 2011.

That program was replaced by the Shaanxi more advanced KJ-200. It was used by China in operations in the South China Sea where in 2017 there was a confrontation between a KJ-200 and a US P-3 Orion maritime patrol aircraft. The radar on the KJ-200 is said to resemble the Saab Erieye radar system.

China has about six different AEW&C programs, including the KJ-500 and a carrier-based version that resembles the US E-2C, the KJ-600.

The Russian AEW&C aircraft that diverted into South Korean airspace is the A-50U model. It is an updated version of the A-50, but lacks an AESA radar. 

Why did Russia intrude? 

The hard-to-answer question is why the Russians diverted the A-50U plane twice to circle around and enter South Korea’s territorial 12-mile limit airspace?

Of the 360 rounds said to have been fired by South Korean F-15s and F-16s, 10 flares and 80 rounds were fired at the first A-50 penetration of South Korean airspace, and 10 flares and another 280 rounds were fired on the second penetration. 

Before that, the South Korean F-15s and F-16s had been challenging the Chinese-Russian operation in their ADIZ, but apparently did not fire off flares or their cannons. 

Both the F-15 and F-16 are equipped with 20mm Gatling gun cannons with a high rate of fire. In a typical warning situation, only a few rounds are fired, if any. In this case, firing 360 rounds is unprecedented, except in a combat scenario.  

The A-50U is unarmed.

Why did the A-50U divert from the Sea of Japan Operation to twice penetrate South Korea’s airspace?

This double intrusion by Russia’s unarmed surveillance aircraft may have been to send a message to the South Koreans that F-15s and F-16s flying around the Russian and Chinese aircraft was unacceptable to them.

But South Korea had every right to be alarmed by a military operation in its ADIZ. South Korea correctly understood that the Russian-China operation with surveillance aircraft and nuclear weapons and cruise missile-carrying bombers was exceedingly dangerous and was a power play by the two big powers to intimidate South Korea and Japan by operating in their ADIZ areas.

When the South Koreans appeared in force, the Russians took a chance and moved the unarmed surveillance aircraft twice into South Korea’s territorial airspace as a kind of counter-warning. 

If that is the right explanation, it was both illegal under international law and unnecessarily provocative, and could have resulted in the shooting down of the unarmed Russian aircraft.

Just as the Russians and Chinese could claim they were operating legally in the South Korean ADIZ, the South Koreans likewise could operate their fighter aircraft in their-own ADIZ “legally.”  

Russia’s gamble in penetrating South Korea’s territorial airspace was not an accident, or caused by a technical fault. If Russia’s military and civilian leaders thought they could throw their weight around without consequences, perhaps they learned a lesson. 

South Korea laid down a powerful marker – that it will not stand by and be intimidated either by Russia or China, and that it will protect its territory aggressively.