Secretary of State John F. Kerry refused Tuesday to rule out putting U.S. troops on the ground in Syria, saying the president needs to retain the ability to send in forces in very select circumstances as the Obama administration officially began to make its case for retaliatory military strikes on the Assad regime. Testifying to the Senate, Mr. Kerry accused critics of “armchair isolationism” and said there are risks to acting, but that the risks of inaction are even worse. But asked whether President Obama would accept an authorization from Congress that specifically banned putting U.S. troops on the ground...