For the past week, US officials have kept up a flow of leaks to the media suggesting that Syrian President Bashar Assad was on the verge of ordering his army to unleash chemical weapons. The details built up as the week went by, starting with the detection of “unusual movements” of Syrian chemical weapons units, advancing to reports that the Syrians were “mixing precursor chemicals” for the nerve gas sarin and on Thursday, Dec. 6, that bombs had been made ready with sarin gas for loading onto Syrian Air Force fighter-bombers when Assad gave the word. Saturday, Dec. 8, British...