The 104th Air Assault Division was supposed to save the Russian campaign on the left bank of the Dnipro River in southern Ukraine. Instead, the newly-formed division “suffered exceptionally heavy losses and failed to achieve its objectives during its combat debut,” the U.K. Defense Ministry reported. Two months ago, Ukrainian marines from the 35th Brigade motored across the Dnipro and, under the cover of artillery, drones and intensive radio-jamming, secured a bridgehead in the settlement of Krynky on the otherwise Russian-held left bank. It’s a new front in the war—one the Ukrainians hope eventually to exploit in order to push...