Houthis' operated systems are based on the Soviet made surface-to-air 2K12 Kub which employs a two-stage rocket engine and the air-to-air missiles R-73 and R-27T which both have a single stage rocket engine. 2020 Nagorno-Karabakh conflict The Armenian Air Defense extensively employed 9K33 Osa missile systems during the 2020 Nagorno-Karabakh conflict. During the opening days of the war, several videos released by the Azerbaijani military showed several Armenian 9K33 Osa and 9K35 Strela-10 vehicles destroyed by Bayraktar TB2 armed drones, with a number of them destroyed in the following weeks when found on the battlefield. Twelve 9K33 Osa missile systems of Armenian Army destroyed during the Nagorno-Karabakh conflict by Azerbaijani Bayraktar TB2. On 4 October 2020, an Azerbaijani Air force Sukhoi Su-25 aircraft was shot down, by Armenian forces, probably by a 9K33 Osa while targeting Armenian positions in Fuzuli. The pilot, Col. Zaur Nudiraliyev, died in the crash. Azerbaijani officials acknowledged the loss in December 2020, with the 9K33 Osa vehicle possibly using passive detection and shoot and scoot tactics to survive the Azerbaijani suppression of air defenses missions. 2022 Russian invasion of Ukraine Both Russia and Ukraine have 9K33 Osa systems in their inventory. On 23 March 2022, The Washington Post reported that the United States was sending additional systems to Ukraine. On 21 December 2022, the Russian military moved equipments through the southern occupied city of Mariupol including 15 tanks and several SA-8 Gecko systems. Command post PPRU-M1 (PPRU-M1-2) is a mobile command center for a mixed grouping of air defense forces, such as 9K33 Osa and the Tor missile system, 9K22 Tunguska, 9K35 Strela-10 and 9K38 Igla. Upgrades Belarus The 9K33-1T "Osa-1T" was developed by UE "Tetraedr" from Belarus. A SAM system comprises combat assets and technical support means, including the 9А33-1Т TELAR or "Combat Vehicle" (CV), based on the original BAZ-5937 (or the new MZKT-69222) and equipped with a new day/night camera system OES-1T instead of the original day-only 9Sh33 or 9Sh38-2 "Karat"; the 9M33M2 or -3 SAMs, or the new 9M33M3-1 with a range of 20 km; the 9Т217-1T Transportation and Loading Vehicle (TLV); the 9V210-1T Maintenance Vehicle (MV); the 9V214-1T Alignment Vehicle (AV); the 9V242-1T Automatic Mobile Check-up and Testing Station (AKIPS) and the 9F16M2 Ground Equipment Kit (GEK). The T38 "Stilet" is a further development of the Osa-1T. Main components are the TELAR T381 on MZKT-69222 chassis and the new missile T382.