The objective of this study is to examine and summarize the features and consequences of the devastation of cities in southeastern Ukraine by the Russian invaders during the initial phase of a large-scale war. It has been determined that the occupier’s adoption of the scorched earth tactic resulted in the complete destruction of numerous settlements, including dozens of cities within the country. It led to a severe disruption of the state’s territorial planning structure. Mariupol, a prominent socio-economic center of the nation, endured extensive devastation and significant civilian casualties. The article examines the distinctive characteristics of the town’s economic progress, the development of its society, the identity of its population, and its social roles. Special emphasis is given to the establishment of the city’s planning framework in response to economic and environmental factors. The planning structure significantly influenced the enemy’s advance, the positioning of the city’s defenders’ strongholds, and the areas that were destroyed. The authors aim to analyze the socio-economic and demographic situation in the city under occupation, based on the media screening. The city has experienced significant civilian casualties, and both its economic framework and infrastructure have been entirely demolished. The occupiers’ statements regarding the reconstruction of Mariupol can be characterized as propagandistic and primarily consisting of declarations. The governing authorities are actively implementing measures to alter the ethnic composition of the population and its cultural identity. The authors define the large-scale destruction of Mariupol and the extermination of its population as the initial phase of a more intricate process of comprehensive urban transformation, referred to as urban transmutation. The key component of it involves an extensive redesign of the city’s urban foundation, planning, and functional framework, as well as the city’s population with its demographic traits, educational attainment, and cultural identity. The post-war reconstruction of Mariupol should incorporate a reevaluation of its role, as the complete reconstruction of ferrous metallurgy in Mariupol during this process presents major challenges. The city’s reconstruction should prioritize the adoption of cutting-edge technological systems centered around digitalization, green technologies, circular production, and other similar advancements.