Ukrainian President Volodymyr Zelensky and his generals have an artful knack for keeping the Russian military bear off-balance. On Sunday, they renewed their offensive in the Russian Kursk Oblast, once again catching the Russian high command, Kremlin, and many pundits by surprise. Reports of a demoralized Ukrainian army fighting to retain terrain captured during the August Kursk offensive — of which at least 40 percent has been lost — have circulated among western media and Russian milbloggers since November. So too reports that Ukraine’s 155th Mechanized Brigade — trained and equipped by France — was under-resourced in “first person view...