When Russian President Vladimir Putin ordered the country’s nuclear forces to go on high alert last week, he looked down a long table at his defense minister, Sergei Shoigu, who nodded in assent. ... Russian troops’ failure to quickly seize Ukraine, however, has shown Mr. Shoigu’s changes, while real, didn’t create the fearsome fighting force he touted. Poor logistics, flawed strategy and ill-prepared troops mean any victory will be immensely costly, and an occupation hard to sustain. ... “By agreeing to these assumptions and this type of operation, he has essentially thrown the Russian military into a disaster.”