The siege of Mariupol began on 24 February 2022, as part of the Russian invasion of Ukraine, and lasted until 20 May. It saw fighting between the Russian Armed Forces (alongside the Donetsk People's Republic People's Militia) and the Ukrainian Armed Forces for control over the city of Mariupol in southeastern Ukraine.
Source: Wikipedia · CC BY-SA 4.0
The 5th anniversary falls on February 25, 2027.