For four years, Russia has bet on outlasting Ukraine in a war of attrition. Now, as Kyiv’s drones inflict growing damage on both Russia’s army and oil industry, Moscow is finding out that time isn’t necessarily on its side. Russian President Vladimir Putin’s invasion force is making ever-smaller gains at the front line, its losses exceed recruitment, and it is struggling to adapt to a Ukrainian drone campaign pounding its supply routes to its forward positions. Meanwhile, Ukraine’s stretched army hasn’t buckled as Russia hoped and is even pushing back the invaders in places with small counterattacks. Its increasingly capable...