S-400 missile system

The S-400 Triumf (Russian: C-400 Триумф – Triumf; translation: Triumph; NATO reporting name: SA-21 Growler), previously known as the S-300 PMU-3, is a mobile surface-to-air missile (SAM) system developed in the 1990s by Russia's NPO Almaz as an upgrade to the S-300 family of missiles. The S-400 was approved for service on 28 April 2007 and the first battalion of the systems assumed combat duty on 6 August 2007. Its longest-ranged interceptor missile, the 40N6, has a purported range of 400 km. The S-400 can be integrated with the shorter-ranged Pantsir missile system, and potentially airborne radars such as of the Beriev A-50U and Sukhoi Su-35S.

The S-400 has been deployed by Russia, including in Belarus and Syria by China since 2018, by Turkey since 2019, and by India since 2021. The S-400 was deployed during Russian intervention in the Syrian civil war from 2015 until the fall of the Assad regime in 2024. China's People's Liberation Army Air Force purchased S-400 systems in 2014, receiving six batteries beginning in 2018, where its range has the potential to affect the Cross-Strait conflict and the Senkaku Islands dispute. The delivery of S-400s to Turkey, which cited US refusal to sell the upgraded MIM-104 Patriot system, trigged Turkey's expulsion from the F-35 fighter aircraft program. Russia has also deployed its own S-400s to Belarus, including from late 2021.

The first alleged S-400 shootdown occurred on 25 February 2022, the second day of the Russo-Ukrainian war, when a system based in Belarus downed a Ukrainian Air ForceSukhoi Su-27 near Kyiv. In November 2025, Russian officials claimed the first shootdowns of Ukraine-launched ATACMStactical ballistic missiles with the system. India, which purchased systems in 2015 and began receiving squadrons in 2021, claimed to have successfully used it in the May 2025 India–Pakistan conflict. The system is complemented by its successor, the S-500, with a purported range of 600 km, which began service with Russia in 2021.