The fate of Ukraine's entire Donbas region hinges on the strategic city of Severodonetsk, President Volodymyr Zelensky warned overnight, as he called on defenders to push back against Russian advances that have increasingly darkened the outlook for the eastern part of his embattled country.

The war in Ukraine, which entered its 16th week Thursday, has shifted decisively from attempts to capture the capital of Kyiv and northeastern metropolis of Kharkiv to the eastern industrial heartland, where Russia has long fomented separatism and now controls wide swaths of territory.

Kyiv, where missiles struck suburbs and mass graves were discovered earlier in the war, is welcoming back foreign dignitaries as embassies reopen, and Russian forces have been largely repelled around Kharkiv. But Moscow's troops occupy the southeastern port city of Mariupol, where Ukrainian fighters held out for weeks in an underground steelworks complex amid sustained assault, and Kherson, the southern coastal city that was the first to fall.

1. Now, in one of the few points on which Kyiv and the Kremlin seem to agree, the Donbas appears poised to fall unless Ukrainians stage a turnaround — something they have accomplished before in other regions of this fertile land but that is looking more difficult by the day.Severodonetsk in Luhansk, one of two provinces that make up the Donbas, is "the epicenter of the confrontation," Zelensky said in an overnight address Wednesday. 
2. He said Ukraine had inflicted "significant losses on the enemy." But that claim could not be verified and came days after Russian Defense Minister Sergei Shoigu said that 97% of Luhansk had been "liberated" by Russia, a term Moscow uses in line with its description of the war as an effort to save Ukrainians and Russian speakers from a corrupt "neo-Nazi" government.

   “The fate of our Donbas is being decided there," Zelensky said of Severodonetsk, where the two sides have been locked in vicious street battles. Previously, has described Severodonetsk and its sister city of Lysychansk, both along the strategic Seversky Donets River, as "dead cities" laid waste by the grinding war of attrition.

   Fighting was reported across the area Thursday.

   "The enemy fired on our units with mortars, artillery and multiple-rocket launchers," the Ukrainian military's General Staff said in a statement Thursday. "It fired on civilian infrastructure in the settlements of Severodonetsk, Lysychansk, Privillya, Ustynivka, Horske and Katerynivka."

   Approaching the front lines here in Lysychansk, the signs of war were clear.

   Booms, the whoosh of rocket launchers releasing their payloads and the ripping sound of heavy machine guns reverberated in the air. The hours-long artillery duels between Ukrainians and their Russian adversaries had left many parts of Severodonetsk burning Thursday morning.

   Even as fighting begins to engulf parts of Lysychansk, some residents insisted on staying.