President Biden is taking flak for sending cluster bombs to Ukraine, and over the weekend he blurted out the truth that both Kyiv and the U.S. are running low on firepower. So why doesn’t the Commander in Chief unveil a new national effort to expand U.S. weapons production and stocks? “The Ukrainians are running out of ammunition,” Mr. Biden told CNN. “This is a war relating to munitions. And they’re running out of that ammunition, and we’re low on it.” The U.S. has given Kyiv more than two million 155mm artillery rounds, and the Pentagon says Ukraine is burning through...