Ukraine’s allies have provided thousands of armored vehicles, artillery pieces, aircraft and other weapon systems to help the country fight back against Russia’s invasion. But requests for top-of-the-line, NATO-standard battle tanks — above all the German-made Leopard and US Abrams — long went unfulfilled. The US cited training and logistical hurdles and Germany said it would not make such a move alone. Yet there are reasons why Ukraine’s military wants them.