Key point: Russia is a huge country, and a region so vast needs a quick plane to defend it.
During the Cold War, the Soviet Union’ s Air Defense Forces (VPVO) needed a series of heavy interceptors to patrol its massive borders. Most regular “light” fighters like the early MiGs were not up to the task, as they lacked the range and speed to intercept to rapidly climb and intercept supersonic American bombers, who were expected to zoom over the Arctic to drop bombs on the Soviet Union.
As a result, a specialized class of aircraft was created for this purpose. The first was the Tupolev Tu-28 and Tu-128. These aircraft would lay the template for later interceptors: they were large for good endurance, fast, and were armed solely with missiles.
This design was obsolete from the time it entered service in the 1960s, as the B-58 Hustler that was in service at the time could outpace it. However, the MiG-25 “Foxbat” was also in development at the time. This aircraft would go on to become the definitive interceptor of the VPVO.
Blisteringly fast and armed with the massive R-40 air-to-air missiles, the Foxbat stood ready to defend the Soviet Union’s borders against all threats. Its airframe also saw adaptation into more tactical roles, photo reconnaissance and strike versions of the MiG-25 were created for the Soviet Air Force (VVS).
In the 1980s, the MiG-25 was followed up by the MiG-31, which added in a second weapons systems officer on all models and increased the flight performance, radar and weapons of the craft. Early versions also featured a cannon, but this was quickly deleted once it was determined that such extras were not necessary on a pure interceptor.