The Vympel K-13 (NATO reporting name: AA-2 "Atoll") is a short-range, infrared homing air-to-air missile developed by the Soviet Union.

In response, the US Navy rushed to modify 100 ROCAF Sabres to carry the newly introduced AIM-9 Sidewinder missile.

These were introduced into combat on 24 September 1958, when a group of MiG-17s cruised past a flight of Sabres, only for them to be attacked by missiles.

"[5] A subsequent claim was made by Ron Westrum in his book Sidewinder that the Soviets obtained the plans for the Sidewinder from Swedish Colonel and convicted spy Stig Wennerström, and rushed their version into service by 1961 copying it so closely that even the part numbers were duplicated.

[1] In 1962, work started on a semi-active radar homing (SARH) version for high-altitude use, the K-13R (R-3R or Object 320) with 8 km range,[citation needed] similar to the little-used US Navy AIM-9C Sidewinder (carried by the F-8 Crusader).

The R-3U ("uchebnaya", training) was an empty missile body with a homing set, allowing pilots to get used to the aiming of the system.

The R-13M was roughly equivalent to the improved USN AIM-9G Sidewinder, with a new proximity fuse, more propellant for longer range, better maneuverability, and a more sensitive nitrogen-cooled seeker head.

The K-13 in different versions was widely exported to the Warsaw Pact and other air forces, and remains in service with a few smaller nations.

It was first used to intercept USAF UAVs flown from Vietnam and other south east Asian countries to mainland China.