New Delhi, March 3 (TIWN) In the seven days since the conflict began, southern Ukraine has become a critical defensive front against Russia's advances, BBC reported.

Moscow has chosen to lay siege to multiple cities there, viewing the region as strategically vital to the success of the invasion as a whole.  Not only would controlling the coast sever the rest of Ukraine from the sea, it would also create a direct connection between Russian-annexed Crimea and the Russian-speaking Donbas region, BBC reported.  Kherson has a population of 280,000 and is so far the largest city to fall to Russian forces. It sits on the banks of the Dnieper River, giving those in control access to critical canals supplying water to Crimea.  Another large port is Mariupol with a population of 4,30,000, which is being shelled and encircled. If successfully seized, Russia will have established a direct link between eastern Ukraine and Crimea, both of which are already Russian-controlled, BBC reported.