All along the 600-mile frontline, the Kremlin’s invasion forces are exploiting Ukrainian exhaustion and a six-month delay in American military aid. A shock offensive in the Kharkiv region has seen Putin’s troops cross the border for the first time since the 2022 invasion. Villages in the Zaporizhzhya region have been wiped off the map as Russia tries to reverse the gains of Ukraine’s 2023 counter-offensive. But the central Russian effort is focused on Donetsk region, where they are now on the outskirts of the hill-top town of Chasiv Yar. If they capture it, they will be in striking distance of...