OPINION: Patrick Shanahan’s departure plunges the Pentagon into uncertainty

PATRICK SHANAHAN’S decision to withdraw from consideration as defense secretary plunges the Pentagon into uncertainty just as tensions with Iran are spiking. It also reveals another case of bad judgment by President Trump, who chose to install as chief of the nation’s armed forces a man who had no record of military or government service but, it turns out, was trailed by a thick file of family turmoil.

Mr. Shanahan was a longtime Boeing executive when he was nominated by Mr. Trump as deputy defense secretary in 2017. His management...