where russian is advancing most. they seized their first major city kherson. and they ve encircled mariupol, where residents are trapped from shelling. let s focus on south ukraine. russia is targeting these cities for strategic reasons. controlling the south cuts ukraine off from the sea and creates a direct link between russia and crimea, which it anexxed in 2014. you can see from this map, troops are advancing from crimea. let s show you what mariupol looks like it s had hours of sustained shelling. hundreds are feared dead. it s still under ukrainian control, but russian troops surround it. electricity, water and heat supplies have been cut. authorities say, they are hindering food supplies, blocking us like in leningrad.